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Robotics;Notes boasts the largest cast in the Science Adventure series to date, filled with many side characters who all play important roles in the plot at some point or another along with the main characters. Names are in Japanese order (i.e. family name first, given name second).

WARNING: Due to the spoilery nature of the series, spoilers for both this game and prior installments (Chaos;Head and Steins;Gate) will be unmarked!


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The Robotics Club

    Yashio Kaito 
https://static.tvtropes.org/pmwiki/pub/images/kai_27.png
Voiced by: Ryōhei Kimura (Japanese), Clifford Chapin (English), Terri Doty (young) (English)

Our main character. A lazy member of the Robot Club, he is Akiho's childhood friend who is always seen playing the Gunvarrel fighting game named Kill Ballad, in which he ranks fifth in the world. His role in the club is Tanegamachine-3's operator and later, the pilot of Gunvarrel.


  • Always Save the Girl: Though he claims that he's only fighting Misaki to settle their rivalry, it's pretty clear he's doing it to make sure Aki won't die with the rest of humanity as well, as evidenced by their confession scene before the climactic final battle.
  • Beneath the Mask: Though Kai tries not to let it show too often, he genuinely cares very much about Akiho, to the point that he'll always try to do things behind the scenes to help her even at his own expense.
  • Big Brother Instinct: Paired with the above trope, Kai often goes out of his way to help Akiho (but only in ways she won't be able to obviously see) with her goals.
  • Catchphrase: "...but you'll have to beat me in Kill Ballad."
  • Character Development: He starts off apathetic towards life, only caring about spending his days gaming and helping Akiho here and there, not giving a crap about his future. But through being forced to help the Robotics Club members as he searches for the Kimijima reports and genuinely learning to embrace his dream again, he manages to learn how to tackle life with renewed vigor, fighting to save the world and settle things with Misaki once and for all.
  • Childhood Friends: He has been close friends with Akiho since childhood. The two of them experienced the traumatic Anemone incident where they were assaulted with Electromagnetic Waves which gave them both "Elephant Mouse Syndrome", and they have mental attacks from this when they get overly stressed/fatigued. Because of this, the two of them always stick together to help each other when these attacks occur, to the point that Aki says that they're both one in mind and soul.
  • Cursed with Awesome: He has "Elephant Mouse Syndrome", a unique illness caused by his brain being irradiated by Electromagnetic Waves during the Anemone incident. Unlike Akiho, he gets to perceive things in Bullet Time.
  • Deadpan Snarker: Constantly making quips about Akiho's ambitions as well the quirks of Frau.
  • Declaration of Protection: He swore to Misaki that he'd always look after Akiho.
  • Despair Event Horizon: This hits Kaito when Mizuka dies because he wasn't able to save her, combined with Subaru's injury happening at the same time. He takes a long time to recover and has PTSD dreams following the incident.
  • Determinator: After it's revealed that he's been manipulated by both Misaki and Kimijima and the world is at stake, Kai steps up big time to stop the black hole bomb before it's too late. He and the others drive to the airport that is being held up by traffic, hitch a ride on his father's airplane (while also stopping Kimijima from killing Airi), spend a whole day working tirelessly to repair Gunvarrel, and he braves the deadly mech battle against Misaki where he constantly has to zap himself with Electromagnetic Waves to keep up with her, which heavily damages his body and leaves him unable to move afterwards. Not bad for a pro gamer.
  • Dream-Crushing Handicap: Implied. He had a dream of being an astronaut once. One might suppose this dream was before the Anemone incident that gave him stress-induced "Elephant-Mouse Syndrome"
  • Geek Physique: Kai is fairly thin and unathletic, though this is justified because his "Elephant-Mouse Syndrome" makes it so he can't push himself too hard, or else he'll suffer an attack and be immobilized for a day or so.
  • The Gift: He has an ability he likes to call "Slo-Mo", which is caused by his "Elephant Mouse Syndrome" he received from the Anemone incident. It kicks in when he pushes his body to its limits and gets overly stressed/fatigued, allowing him to witness several seconds in real time pass as several minutes for him. This allows him to make frame perfect inputs in real life that would be impossible realistically, and is what allows him to defeat Misaki at the end of the game and save the world.
  • Godlike Gamer: He's spent so much time playing Kill Ballad that he's become 5th in the world rankings wise, and most of the playerbase knows who he is. By the end of the story he rises to 2nd place, and then finally claims 1st when he defeats Misaki at the end of the game.
  • Good Is Not Soft: Though he grows to care for his comrades in the Robotics Club and learns not to give up on life, he does not take kindly to Kimijima manipulating him. He fights tooth and nail to stop him and Misaki, and puts them down hard.
  • The Hero: Though he very much doesn't seem like it at first, he ends up coming into his own and becomes the unexpected hero the world needed to stop the Black Hole Bomb by the end.
  • Hidden Heart of Gold: Kai acts aloof in front of his friends, but behind the scenes he goes out of his way to keep Aki happy.
  • Iconic Item: His Pokecom/Phonedroid, which he can be seen always playing Kill Ballad on whenever he has downtime.
  • I Know Mortal Kombat: His robot-controlling and later, mecha-piloting skill. Justified, since the controller is specifically made to resemble the Kill Ballad console.
  • I Let Gwen Stacy Die: Kai blames himself for not being able to save Mizuka from being killed by her HUG in Phase 9, and this guilt sticks with him for the rest of the game as he has PTSD dreams about what he could've done differently following the incident.
  • Jerk with a Heart of Gold: He acts very dispassionate and rude to most people he meets, but for the people he truly cares about, he'll go to hell and back for them, such as Aki.
  • Lazy Bum: One of his reasons for joining the Robotics Club is so he can freely play Kill Ballad in the clubroom.
  • Like Brother and Sister: Him and Akiho's relationship for most of the game, until the two of them finally profess their love for each other at the end.
  • Loophole Abuse: At the end of the game, he figures out that he can hit himself with Electromagnetic Waves using the Noah IV device to trigger his Slo-Mo ability (which he received because his brain was irradiated by EM Waves as a child) which he normally can't use on command. Using this, he's able to keep up with Misaki in the mech battle without sustaining too much damage that would immediately kill him, and manages to win the day as a result.
  • My Greatest Failure: How Kai feels about failing to save Mizuka from inadvertently killing herself when her HUG acts out against her.
  • Nice Job Breaking It, Hero: Kai plays into Kimijima's trap easily and allows the Kimijima reports to be shared around the planet, which allows the Committee to deceive and cause massive panic worldwide so they can unsuspectingly shoot out a BHB that will destroy the world.
  • Not So Stoic: He finally shows an emotional outburst to Aki in Phase 11 in order to get her out of her Heroic BSoD. Aki even notes that he's not acting like his usual self.
  • Oblivious to Love: He seems to not notice Akiho's feelings for him until near the end of the game.
  • Only I Can Kill Him: Kai embodies this at the end of the game when he says the only reason that he's fighting so hard is because he wants to settle things with Misaki and prove once and for all that he's surpassed her after all of these years, settling their childhood rivalry.
  • Platonic Life-Partners: With Akiho, until their Relationship Upgrade in Phase 12 when they confess to each other.
  • Retired Badass: At the end of the story he stops playing Kill Ballad regularly, and goes on a trip to study to become an astronaut, his childhood dream.
  • Sarcastic Devotee: Before Subaru took the role, he was the one who primarily shot down Akiho's ideas. Nevertheless he always does his best to help her no matter what suffering awaits.
  • Savvy Guy, Energetic Girl: With Akiho, again. Subverted during Episode 18 when even he goes genki.
    Akiho: As swift as the wind and as spirited as the storm seas! GUNVARREL!!! Ka-ching!!! XD
    (camera pans to everyone else who has the same expression)
  • Self Harm Induced Super Power:
    • He spends all of Phase 7 with Frau trying to inflict different tortures on his body in order to become fatigued enough to activate his Slo-Mo.
    • On the day of the final battle, he discovers that he can use Noah IV's function of shooting out Electromagnetic Waves to hit himself and forcefully activate his ''Elephant Mouse Syndrome.''
  • Serious Business: He will always take a match of Kill Ballad very seriously, never going easy and always trying his hardest to win the match. Subverted when he gives up his win streak to prove to Aki that he'll be by her side to the very end, no matter what happens.
  • Stepford Snarker: By the second half of the story, he's witnessed some traumatizing events such as Frau attempting to kill herself as well as Mizuka's death, yet still covers it up with sarcasm. Akiho calls him out on it.
  • Straight Man: He's always this to the rest of the Robotics Club. He always takes the piss out of Aki's enthusiasm, Subaru's stoic attitude, and he always shuts down Frau's horny antics whenever she tries to shove them down his throat.
  • Supporting Protagonist: He's the main character but primarily focused on helping Akiho with her ambitions and surpassing her sister.
  • This Looks Like a Job for Aquaman:
    • Is the best person to operate the robots since they programmed the controller to be like a Kill Ballad game pad. Though this is Inverted in that he refuses to control any robot that doesn't use a Kill Ballad game pad.
    • Later, to stop robots rampaging in Tokyo, someone has to beat an extremely difficult round of Kill Ballad.
  • Took a Level in Badass: Dude manages to pilot a dangerous mech and survive a mech battle with the power of sheer determination and Electromagnetic Waves constantly zapping him so he can survive by the skin of his teeth, and he manages to save the world in doing so.
  • Trademark Favorite Food: Eats "Space Candy" when he's ready to get serious.
  • Unwitting Instigator of Doom: It's because Kai goes out of his way to collect all of the Kimijima reports and spreads them to the rest of the world that Kimijima can enact his plan of deceiving and misinforming the entire world to the point of throwing everyone into a mass panic, which allows for the Black Hole Bomb to nearly be fired off without being noticed.

    Senomiya Akiho 
https://static.tvtropes.org/pmwiki/pub/images/aki_2.png
Voiced by: Yoshino Nanjo (Japanese), Lindsay Seidel (English)

The Deuteragonist of this story. She is the President of Tanegashima High's Robot Club which her sister, Misaki Senomiya, founded. A very energetic and optimistic tomboy, Akiho's goal is to finish the Gunbuild-1 project, a project to build a real-life Humongous Mecha that the club started eight years ago.


  • A-Cup Angst: Implied to be the reason she hates when Mitchie calls her "Little".
  • Always Someone Better: A gifted roboticist, but firmly believes her skills pale in comparison to her older sister's.
  • Break the Cutie: Many bad things happen around her, such as the principal attempting to disband the Robotics club, or her sister cutting off all contact with her and later destroying Gunbuild 2 despite Akiho's attempts to protect it. Were it not for Kaito hanging around her, she'd probably suffer a massive Heroic BSoD which she probably couldn't recover from since he helps her quite a lot behind the scenes despite protesting the things she does.
  • Calling Your Attacks: Loves to do so while watching robots fight, even during the RoboOne tournament. Lampshaded by Kaito.
  • Catchphrase: She actually has three main ones!
    • "Storm and surge!"
    • "Blast of spirit!"
    • "Yoira-iki~!"
  • Childhood Friends: She has been close friends with Kai since childhood. The two of them experienced the traumatic AMF nemone incident where they were assaulted with Electromagnetic Waves which gave them both "Elephant Mouse Syndrome", and they have mental attacks from this when they get overly stressed/fatigued. Because of this, the two of them always stick together to help each other when these attacks occur, to the point that Aki says that they're both one in mind and soul.
  • Clingy Jealous Girl: Shows shades of this in Phase 2 when Kaito mentions going somewhere with Junna, and again later on when Kai mentions hanging out with Nae but it's ultimately averted as she respects Kai's wishes to do as he pleases.
  • Cloud Cuckoolander: Has shades of this, and sometimes goes off on a tangent about things almost seemingly at random at times.
  • The Confidant: Surprisingly subverted. While she and Kai grew up supporting each other and such, Kai refuses to tell her about the conspiracy he's learning more about that's surrounding them. She constantly tries to get him to open up to her since she can tell that he's obviously hiding something that's bothering him, but he refuses, and before he knows it it's already too late.
  • Determinator: Though she's not as good as the other members in their specialties, her enthusiasm for building a mech helps hold them together. Kaito allows her to defeat him in a Gunvarrel game after she demonstrates this trope, and tells him why they need to work on building a mecha and thus get his help. Prior to that, he would always easily beat her in the game any time she tried.
  • Deuteragonist: Easily the character with the 2nd highest first person perspective screentime in the story, and she's also the one who drives the majority of the plot, constantly pushing to build Gunbuild 1 and 2, and never giving up on it to the very end. It's because of her tenacity and attitude that Gunbuild manages to be completed, and is able to be used to fight off the Committee's latest plan and save the world. Without her, the world would've been doomed. This is just as much her story as it is Kai's.
  • Expy: Considered to be the Okabe analogue in the series with her constant enthusiasm, only with robots instead of time machines.
  • Fangirl: Of robots and mecha. If it wasn't obvious.
  • First Girl Wins: As the first girl to appear in the plot and Kai's childhood friend, she ends up being the one to get together with Kai at the end of the story.
  • Genki Girl: Played very straight. Akiho is very energetic and bold, always trying to recruit people in the club. Given the fact that the club has only two members though, she isn't very successful.
    • She focuses so hard on her upbeat attitude because she feels it's her only good trait, as she has a severe inferiority complex of believing she's not good enough due to how often she's compared to her sister's achievements as well as her sister's last words to her putting her down and making her believe she'll always be average.
  • Genius Ditz: Prone to do silly things she might be, but Akiho is a good mechanic.
  • The Heart: She's the most energetic and emotionally driven of the Robotics Club, and the glue that holds most of them together that focuses on achieving their goal.
  • Heroic BSoD: Suffers a minor one in Phase 9 when the Robotics Club is disbanded, and a major one in Phase 11 when Misaki destroys all of the robots at the Expo, including Gun-Build 2, and nearly kills her and Kai.
  • The Heroine: Kai takes a very passive role for a majority of the plot, and it's only thanks to Aki that the club even comes together to begin with. She spearheads the building for Gunbuild 1 and 2, gathers all of the club members together, and eventually succeeds in building her robot and getting them to the Robo EXPO. She's also a large part in how the aforementioned giant robot is able to become functional enough to fight in battle and save the world at the end of the story.
  • Honor Before Reason: She is hellbent on constructing Gunvarrel even though the task is simply impossible with Robotics Club's resources.
  • Hot-Blooded: She loves imitating the hot-blooded Super Robot pilots of her favorite anime - so much that her catchphrase is the attack name of the mecha from the Show Within a Show.
    "Gunvarrel Ankh STRIKER!"
  • Humble Goal: Wants to finish constructing the Gunvarrel robot her sister started.
  • Justice Will Prevail: A firm belief she holds thanks to the uplifting Mecha anime she watched growing up as a kid.
  • The Leader: A combination of charisma and determination make her the ideal leader of the club.
  • Locked Out of the Loop: Kai refuses to tell her anything about the Kimijima reports, so she's completely unaware that there's a world ending conspiracy looming around the corner until it's too late and she and Kai are negatively affected by its events finally coming to fruition.
  • Letting Her Hair Down: Phase 10, when she's sleeping with Kai during the expo.
  • Official Couple: At the end of the game, Kai and Aki finally express their love for one another right before the final battle, and presumably begin to date after the battle as they graduate.
  • Platonic Life-Partners: With Kaito, until their Relationship Upgrade in Phase 12 when they confess to each other.
  • Plucky Girl:
    "My only virtue is that I'm stupidly positive!"
  • The Pollyanna: Tries to be this even as things largely go downhill around her from time to time.
  • Proud to Be a Geek: She relishes in being a tomboy who's unapologetic about her love for Mecha Anime, and she makes sure that everyone knows it, spouting [[Anime/Gundam Gunbam]] references left and right.
  • Purely Aesthetic Glasses: When she puts her glasses on, expect a Shout-Out to Gundam.
  • Red Oni, Blue Oni: She is the red to everyone else's blue.
  • The Scrooge: Aki can be quite stingy with money. Later, when she learns about the monopole, the first thing Aki wants to do is sell it for money to buy more robot parts.
  • Throw the Dog a Bone: After being constantly beaten down for most of the story with everyone discouraging her and trying to stop her from achieving her dream, with the help and the rest of the Robotics Club she manages to finish building Gunbuild 1 and gain the respect/love of all of her peers, finally proving to herself and the world that she's just as competent as her successful older sister.
  • Trademark Favorite Drink: She loves Skal to death!
  • Wrench Wench: She is often seen wearing mechanic coveralls and actively working on the Gunbuild 1 and 2.

    Hidaka Subaru 
https://static.tvtropes.org/pmwiki/pub/images/subaru_9.png
Voiced by: Yoshimasa Hosoya (Japanese), Jarrod Greene (English)

A second-year student in the same school as Kaito and Akiho. A brilliant roboticist, Subaru's skills allowed him to win the Robo-One championship, but he did so under the disguise of his "Mr. Pleiades" persona so his father would not be upset with him. Kaito later blackmails him to join the Robotics Club.


  • Abusive Parents: Zig-zagged. His father is not normally violent, but he does hit him once he discovers that Subaru lied to him and broke his promise not to give up being involved with Robotics building.
  • Conflicting Loyalty: Wants to be loyal to his father, but still remains in the Robotics Club to help his friends.
  • Cool Mask: As Mr. Pleiades.
  • Foil: To Akiho. Both are passionate about robots, but while Akiho is idealistic, Hot-Blooded and peppy, Subaru is realistic, calm and sour.
  • Incoming Ham: He have a habit of tilting his glasses when trying to inform people of things he considers obvious and realistic.
  • Jack of All Stats: While not as skilled an operator as Kaito, not as brilliant a programmer as Frau and not as ambitious a roboticist like Akiho, Subaru is no slouch in any category.
  • Keeping Secrets Sucks: This ham is almost too large for its packaging! Too bad using this persona means he's going back on his word to his father, whom he looked up to.
  • Large Ham: As Mr. Pleiades, just look at his outfit!
  • Luminescent Blush: He's actually quite shy about physical contact with girls.
  • Not So Above It All: He seems like a serious student, but his Mr. Pleiades disguise shows that he can be just as silly as Akiho.
  • Only Sane Man: Most of the time he acts as this to the rest of the Robotics Club, especially if Kaito isn't around.
  • Sour Supporter: Is reluctantly brought on board with the Robotics Club, and often criticizes what Akiho is doing, such as making Gunbuild 1 too heavy to move with the small motors it has on it. Despite that however, he does offer good advice when given the opportunity for input.
  • Speech Impediment: When he's nervous, he can't talk straight.
  • This Is My Name on Foreign: Kaito points out that "Subaru" is the Japanese way of saying "Pleiades" the star cluster.
  • Verbal Tic: Whenever he gets flustered, he usually slurs and mispronounces his words in embarrassment.

    Daitoku Junna 
https://static.tvtropes.org/pmwiki/pub/images/junna_4.png
Voiced by: Sora Tokui (Japanese), Monica Rial (English)

A member of the Robot Club who practices karate. Junna was initially reluctant to join due to being afraid of robots, though was encouraged to join by Kaito. She has a fear of robots that has plagued her since childhood. She is also the granddaughter of Fujita.


  • Audience Surrogate: Probably the most normal character of the cast with practically no experience with robots.
  • Covert Pervert: She may be easily flustered, but she was still the one to think of the photoshoot as a African safari when she misheard "Cheaters" as "Cheetahs".
  • The Ditz: Zig-zagged. She's very innocent, especially in regards to the lewd remarks Frau tends to make about her, but she's not stupid.
  • The Face: She basically becomes the poster girl of the Robotics Club's sponsors, Space Candy, because Sumio loves how she looks and the way she acts with her Kata.
  • Face Your Fears: The crux of her character route is how she's unable to truly face her grandfather or any robots because of a traumatic incident in her past. Once she realizes that her grandfather killed his dream to atone for her traumatic incident however, she desperately works to reconnect with him and restore the dream that he so dearly loved, and succeeds, becoming a stronger person for it.
  • I Know Karate: She practiced Karate for years, though she was never truly able to get past her first few matches in the few tournaments she attended. She still practices her kata however, as it's soothign to her.
  • Imagine Spot: Prone to getting ones about... questionable topics.
  • My God, What Have I Done?: A strong wind topples the Gun Build-2 onto Subaru while she was operating it. He is badly injured and Junna blames herself.
  • Not Quite the Right Thing: When she was a child, one of her grandfather's robots fell on top and her and soon her grandfather arrived and started yelling. Despite what she thought at the time, her grandfather was really yelling at the robot for scaring her.
  • Purity Personified: Junna is easily flustered by Frau's dirty talk and tends to panic about female decency.
  • The Quiet One: Easily the least talkative Robotics Club member.
  • Shrinking Violet: She's very shy and easily flustered.
  • Single-Issue Psychology: She had a traumatic experience involving a robot nearly crushing her to death as a child and as a result is terrified of them. This incident also led her to becoming estranged with her Grandpa Fujita who she believes hated her for damaging his robots, when he really was angry at himself and his robots for hurting her.
  • Verbal Tic: She has a habit of accidentally misspelling words in her Tweeps.

    Koujirou Frau 

Furugoori Kona

https://static.tvtropes.org/pmwiki/pub/images/frau_5.png
Voiced by: Kaori Nazuka (Japanese), Leah Clark (English)

Resident Hikikomori and the socially inept creator of Kill Ballad, the wildly popular fighting game based on the Gunvarrel anime. A brilliant programmer, Frau is the daughter of the Director of Gunvarrel, who was accused of murdering the entire Gunvarrel staff although the details of which are even more complicated. Her mother disappeared shortly after and Frau has been searching for her since.


  • Adaptational Badass: Appears as a playable guest character in Phantom Breaker: Battle Grounds, a spin-off Beat 'em Up to the Fighting Game Phantom Breaker. She's more than capable of taking down her bizarre opponents using several remote-controlled robots, or with help of other characters from the visual novel.
  • Ambiguous Disorder: Frau checks off a lot of the boxes for an Autism Spectrum Disorder: she is a hikikomori who appears to have genuine trouble interacting with other human beings face to face (acting very inappropriately and randomly acting either very averse to or forcing physical contact against their will), has some sort of speech impediment (appears either uninterested in or incapable of matching the volume of her voice to social context, and randomly shouting inappropriately sexual words, swearwords or internet slang), changes her facial expression rarely, extremely, and without relation to context (so she might appear completely expressionless throughout an entire conversation, suddenly laugh out loud for no reason, grin insanely, then just as quickly return to looking bored), considers her best friends to be cartoon characters and is as superhumanely talented with computers as she's inept at every life skill which doesn't involve them.
  • Anime Hair: Her pigtails defy gravity when they're tied up.
  • Catchphrase: ''But I refuse!''
    "Pant pant What eroge is this?!"
  • Child Prodigy: She is the creator of Kill Ballad.
  • Evil Laugh: "Duhuhu..."
  • Forgets to Eat: As a result of her obsessive work habits. This is a recurring problem for her that forces Kaito to visit to feed her regularly.
  • Freudian Excuse: Her mother being the accused killer of what was her favorite anime crushed her and led to her hikikomori status. She spent all of her time shut-in to develop Kill-Ballad in honor of her mother's work fo Gunvarrel.
  • G.I.R.L.: Kaito initially assumes she was a guy using a female name at first.
  • Human Mail: She "mails" (not with the Japanese Postal Service, but Mitsuhiko, but it still counts) herself to her new home, along with all her stuff.
  • Hikikomori: Upon moving to Tanegashima, she spends most of her time holed up in her room with her PC, and constantly skips classes.
  • Hyper-Competent Sidekick: While she surely doesn't seem like it at first, she basically becomes Kai's only confidant in regards to the Kimijima reports and being as knee-deep in the conspiracy as he is. Her programming skills and resourceful researching helps him to better understand the gravity of the conspiracy they're in, as well as help him in other areas such as hacking IRUO to help Airi and allowing him to control Gunbuild 1 with a program that mods the controls to be like Kill-Ballad.
  • Leet Speak: Speaks like she is posting to an Imageboard.
  • Lovable Sex Maniac: Frau's mind is about as clean as a septic tank.
  • Missing Mom: Frau's main motivation for moving to Tanegashima is to search for her mother, who went missing 4 years prior after the final episode of Gunvarrel failed to air. It is confirmed in the Visual Novel by a Twipo comment chain that her mother was killed by the Committee.
  • Otaku: A textbook case of the Fujoshi variety at that.
  • Otaku Surrogate: Specifically for those into the yaoi and moe genres.
  • Shipper on Deck: Apparently ships Kaito/Subaru, although this might have more to do with her Yaoi Fangirl tendencies.
  • Slasher Smile: Especially when she's around Junna.
  • Smarter Than They Look: While she seems like nothing more than a horny shut-in fujoshi, she's incredibly talented and not stupid. She just uses her otaku tendencies to cover up the pain she feels inside and acts like things are alright when they're really not for her.
  • Speech Impediment: She has a heavy stammer that comes out when she's riled up.
  • Teen Genius: She's a gifted programmer who made one of the most popular fighting games of all time in middle school.
  • Unkempt Beauty: She's incredibly messy and often has her hair not tied up, but she definitely has many fans who love her appearance regardless.
  • Yaoi Fangirl: She claims to have at least a terabyte of pornographic BL thinbooks, and isn't afraid to proposition Subaru for more. She also constantly ships Subaru and Kai together, much to their dismay.

    Airi 

Sister Centipede

https://static.tvtropes.org/pmwiki/pub/images/airi_7.png
Voiced by: Rie Kugimiya (Japanese), Apphia Yu (English)

A dual program within the IRUO app, acting as the AI interface. She dictates everything about the Kimijima Reports, from its instructions to the actual details, even though she really doesn't know what they actually mean. Sister Centipede is the main AI, and she's the one who makes the actions. Airi is actually a Littlest Cancer Patient given extra time to live her life by Kou Kimijima.


  • Artificial Human: She's an AI that can only be seen by using the iPod-like devices that act as phones and the consoles everyone plays Kill Ballad on.
  • The Cutie: Standard Airi.
  • Deadpan Snarker: Sister Centipede, oh so very much. She loves to say "Chill Out" and shut down Frau's horny tangents, something she definitely inherited from her childhood years spending time with Takumi from Chaos;Head in ESO, 2009.
  • Grew Beyond Their Programming: Sister Centipede manages to turn against Kimijima, unable to bring herself to harm Kaito and the real Airi, though she believes this to be a bug in her programming.
  • Heroic Sacrifice: Sister Centipede manages to save Kai, Nae and the real Airi from being killed by Kimijima's robot assault, but is deleted by him in the process, saying a tearful farewell to the real Airi in the process.
  • Littlest Cancer Patient: Airi is actually a frail girl who was given an extended life within IRUO from the original author. Unfortunately, she had only another year left to live.
  • Ms. Exposition: She explains a decent amount of the Kimijima reports and how to find them to Kai.
  • Mundane Luxury: More than anything else, Airi wants to see snow.
  • Mysterious Waif: Complete with white hair.
  • Red Oni, Blue Oni: Respectively Airi and Sister Centipede.
  • Split Personality: Kaito can manually invoke this by tapping her forehead. Sister Centipede is more straightforward with her explanations than the playful Standard Airi.
  • Suddenly Always Knew That: Real Airi somehow has access to Sister Centipede and Standard Airi's knowledge of Kimijima's inventions despite not understanding it herself. She also inherits Sister Centipede's knowledge of certain lewd topics that she learned of during her time spent with Takumi.
  • Wetware Body: Real Airi is later possessed by Kimijima's cyber ghost.
  • Your Days Are Numbered:
    • Real Airi was dying of disease before Kimijima made her a Human Popsicle.
    • Standard Airi similarly knows she will be deleted when the IRUO network she lives in undergoes maintenance on Christmas Eve.

Other Characters

    Senomiya Misaki 
https://static.tvtropes.org/pmwiki/pub/images/misaki_11.png
Voiced By: Kikuko Inoue (Japanese), Caitlin Glass (English)

The previous leader of the Robotics Club, Misaki now works for EXOSKELETON as the company's spokeswoman and investigates the Kimijima Reports behind the scenes. Once an idealistic and energetic girl, Misaki has grown aloof and detached, never even keeping in touch with her sister, Akiho. Misaki murdered Kou Kimijima after learning of his genocidal plan. She would later be possessed by Kimijima's cybernetic ghost, becoming a pawn in the scheme she tried so desperately to prevent.


  • The Ace: While in high school, Misaki was an extremely skilled roboticist, a talented engineer, won the Robo-One tournament, and regularly defeated a young Kaito at video games.
  • Break the Cutie: Kou Kimijima's Virtual Ghost continued to haunt her even after his death and threatened her to expose her murder of him, which eventually drove her into this.
  • Damsel in Distress: She's basically been mind hacked by Kimijima and unable to fight off his will, so it's up to Kai to break her free of her mind control and free her from the hell she was forced under, which he manages to accomplish in their climactic final battle.
  • Gamer Chick: As she grew up with Kai and Aki, she'd always play fighting games with Kai and beat him senselessly in them.
    • It's revealed by Sawada that even as she got older, she would often play Kill-Ballad on her downtime and is ranked as the top number one player in the game under a username. Kai would often trade blows with her.
  • Evil Costume Switch: When he true colors are revealed, she dons a dark purple jumpsuit reminiscient of G Gundam pilot suits in order to pilot a HUG mech. She then goes with an elite squad of Committee assailants to detain and secure JAXA's building and all the people inside, including her own father, holding them at gunpoint.
  • Genki Girl: Comparable to that of Akiho when she was younger, which makes sense given they had similar upbringings with their father raising them on Mecha anime that gave them both energetic tomboyish personas.
  • Meat Puppet: Kimijima's way of punishing her for stopping his plans.
  • Powered Armor: Gets a cybernetic suit that increases her agility and strength.
  • Proud to Be a Geek: Much like Akiho, everyone knew her to be a determined tomboy that was very passionate about her love for Mecha Anime, to the point that she started the Robotics Club all on her own.
  • Retired Badass: Well, from Robo-One tournaments, anyways.
  • Yamato Nadeshiko: When she was in high school.

    Irei Mizuka 
https://static.tvtropes.org/pmwiki/pub/images/mizuka_9.png
Voiced By: Takako Honda (Japanese), Lydia Mackay (English)

The owner of a local convenience store and a motherly figure to Kaito and Akiho. Mizuka is very knowledgeable about Tanegashima and various rumors that circulate the island. Her legs were paralyzed from a motorcycle accident, and, some time later, was given prosthetic robotic legs from Misaki.


  • Blood from the Mouth: Happens when the robotic exoskeleton that helps her walk goes out of control and forcibly straightens her spine up.
  • Curiosity Is a Crapshoot: Warns Kai not to delve into the Kimijima Reports.
  • Cruel and Unusual Death: She has her back brutally broken by her HUG unit and is forced to walk off a cliff, falling falls onto many rocks that fatally wounds her. She succumbs to her wounds shortly after.
  • Eat That: Challenges anyone who needs information to buy and eat a revolting cheese/passionfruit-filled, spicy nikuman. Better eat it fast.
  • Knowledge Broker: Kai often goes to her for information on things that'll help him either help Akiho or learn more about the people in his life so he can further help them, though she forces him to buy and eat a Passion Fruit before he'll inform him of what he wants to know.
  • Powered Armor: The exoskeleton around her legs help her walk now that after she was paralyzed by a car accident.
  • Secret-Keeper: She took the secret of what she clearly knew was Misaki's murder of Kimijima to her grave.
  • She Knows Too Much: She has a pretty good idea of what happened to Misaki the night that Aki and Kai nearly died in the Anemone Incident, and she tries to warn Kai multiple times to stop following the Kimijima reports. When she finally confronts him in a last ditch effort to get him to get out of the conspiracy before it's too late, Kimijima purposefully hacks into her Pokecom and remotely controls her HUG, forcing her to walk off a cliff and fatally injuring her. She dies in the hospital afterwards.
  • Walking Spoiler: Talking about her role in the story is a very easy way to give away that she's murdered near the end.

    Doc 

Fujita Tetsuhara

https://static.tvtropes.org/pmwiki/pub/images/doc_6.png
Voiced By: Nobuaki Fukuda (Japanese), R. Bruce Elliott (English)

The grandfather of Junna who runs the local robotics shop. He supplies the Robotics Club (both past and present) with the parts they need. His expertise in creating robots is one of the greatest. He also loves blasting Heavy Metal in his shop.


  • In-Series Nickname: "Doc"
  • Jerk with a Heart of Gold: He's rough around the edges, but the man loves his granddaughter and looks out for Akiho, too.
  • Mr. Vice Guy:
    Doc: "Here, I also got you a gyro and other necessary parts. You'll need these if you want to win."
    Akiho: "Doc... tha-"
    Doc: "That'll be 15,000 altogether!"
  • My Greatest Failure: His love of robots indirectly lead to Junna nearly being crushed by one and scarring her for life. It takes Kai and Aki's efforts of rebuilding his robots and Junna reaching out to him once more for him to re-embrace his dream of allowing Robots to be kind and give joy to children and adults alike.

    Tennouji Nae 
https://static.tvtropes.org/pmwiki/pub/images/nae.png
Voiced By: Ayano Yamamoto (Japanese), Brina Palencia (English)

You may know her as the daughter of a certain CRT-TV shop owner, but she's now a scout and engineer of JAXA, the Japanese equivalent to NASA. After an initially shaky agreement, she provides funds to the robotics club and, later on, the temporary usage of a JAXA hanger for the usage and testing the robot.


  • Badass Adorable: She has some pretty mean close combat moves, which she uses to take out several armed commandos trying to capture Frau.
  • Big Damn Heroes: She ends up saving the day by taking out the Committee priests who tried to pin down and kidnap Frau to prevent her from interfereing with their plan to launch the Black Hole Bomb into space.
  • Expy: An energetic Action Girl who rides her bike everywhere... Looks like Suzuha rubbed off on her.
  • Gamer Girl: In Phase 5, she starts playing Kill-Ballad with Kai on a regular basis and ends up matching his skill by the end.
  • Genki Girl: Not Aki's level, but she sure likes to shout when she's excited. Complete with Fist Pump.
  • Girlish Pigtails: Still wears them as an adult.
  • Japanese Politeness: Nae is always gratuitously polite.
  • Kidnapped by the Call: Her Establishing Character Moment is abruptly abducting the cast before offering them the chance to work with JAXA.
  • She Is All Grown Up: She was only 11 years old in Steins;Gate, and now in Robotics;Notes she arrives in Tanegashima as a 20 year old engineer for the Japanese Space Program (JAXA). Notably, she seems to have mastered Suzuha's martial arts by the time: she even uses some of the same, iconic moves to defuse a similar hostage situation.
  • Sixth Ranger: For the Robotics Club.

    Mitchie 

Nagafukada Mitsuhiko

https://static.tvtropes.org/pmwiki/pub/images/mitchie.png
Voiced By: Yoji Ueda (Japanese), Robert McCollum (English)

A teacher from the main characters' school and the advisor of the Robotics Club. Mitsuhiko was himself once a member of the Robotics Club alongside Misaki. He's a jolly guy, though he rarely gets any respect from Akiho due to his... lazy habits. Aki and Kai refuse to call him "Senpai" and just nickname him "Mitchie."


  • Adults Are Useless: Averted, but no one seems to think any better of him regardless.
  • Cool Teacher:
    • Subverted. He seems pretty unreliable, to the point that Kai and Aki constantly point out how useless he is.
    • Played straight when he becomes much more responsible after Mizuka's death, to the point that the man risks life and death to drive Aki and Kai to the airport during what most people believe is a solar storm, in order to help them save the world.
  • Diving Save: When Aki falls from a ladder, Mitchie (surprisingly enough) is the one to heroically break her fall.
  • Dude, Where's My Respect?: When the chips are down, Mitchie usually comes through. Though, Aki only ever seems to remember the things he's done wrong.
  • In-Series Nickname: "Mitchie"
  • The Nicknamer: Calls Akiho "Little Senomiya."
  • Shipper on Deck: Likes to tease Aki and Kai a lot.

    Nagafukada Sumio 
https://static.tvtropes.org/pmwiki/pub/images/sumio_93.png
Voiced By: Tetsuo Kanao (Japanese), David Wald (English)

Mitsuhiko's bulky uncle and the president of Space Ame, the company that makes the ''Space Candy" Kaito is so fond of. Sumio funds the Robotics Club's projects in exchange for publicity and Space Ame's logo is displayed on the club's robots.


    Sawada Toshiyuki 
https://static.tvtropes.org/pmwiki/pub/images/sawada_1.png
Voiced By: Shin-ichiro Miki (Japanese), Chuck Huber (English)

The mysterious CEO of EXOSKELETON, the company that develops Power Suits among other robotic projects, and Misaki's supervisor. Sawada is also a member of a secret organization that opposes the Committee of 300 despite Sawada being the son of one of the higher ranking Committee members.


  • Archnemesis Dad: Will not rest until he has stopped Project Atom and the Committee of 300, which includes his father.
  • Big Good: He was actually working for the Anti-Committee group this entire time, trying to undermine their efforts as best he could.
  • Brick Joke: It's no wonder he wanted to leave the Committee of 300. They were involved with Chaos;Head's premise.
  • Dark Is Not Evil: He certainly looks and sounds like your typical evil, conniving businessman, but Sawada is actually on Kaito's side.
  • Stab the Scorpion: Looks like he's about to pull the trigger on Kai and Aki, he actually shoots at Misaki.
  • Walking Spoiler: Any in depth discussion about his character will reveal that he's actually a good guy and not the main Committee villain of this game.

    Kimijima Kou 
https://static.tvtropes.org/pmwiki/pub/images/kimijima.png
Voiced by: Toshiyuki Morikawa (Japanese), Eric Vale (English)

The author of the Kimijima Reports, who died 9 years prior to the events of the story.

It turns out that he works for the Committee of 300 and caused the Anemone incident which was in fact an experiment that would have killed all the test subjects via electromagnetic waves irradiating their brains. This was stopped by Misaki Senomiya, who was forced to kill him in the process. However, before his death he uploaded his consciousness to the internet and lives on through IRUO, and now plans to execute the Committee's plans by inducing a massive solar flare that will kill the majority of the population of Earth. He uses the Kimijima Reports to manipulate people, and he has Sister Centipede and Misaki (who was brainwashed by him) do his bidding in the the virtual and real worlds respectively.


  • Cybernetics Eat Your Soul: Airi mentioned that he wasn't always obsessed with the experiment and did want to help her. However, he lost that human conscience/restraint when he was turned into an AI that was uploaded to the net. Now he'll stop at nothing to achieve this goal for the Committee.
  • Graceful Loser: When faced with a digital missile to the face, he starts out saying that there will be more of him eventually. Kai just tells him that even so, those who fight back will still win. He accepts this and goes out with a smile.
  • Pet the Dog: His short time with Airi may or may not be this. The flashback scene at one episode as well as Airi's words in episode 21 implied that his treatment on her was genuine, but his words in the previous episode also implied that she was merely a test subject for his consciousness-uploading experiment.
  • Only Mostly Dead: Was killed by Misaki. However, he uploaded his consciousness on the net before this happened.
  • Walking Spoiler: Talking about him in detail reveals that he's the real Committee villain of this game.

    Twipo Users 

Lightning-Fast Neidhardt

An odd twipo user that Kai is introduced to by Sister Centipede in Phase 7. He's actually the former protagonist of Chaos;Head, Nishijou Takumi, now 27 years old and part of the Anti-Committee group resistance that was formed by the Black Knights and Future Gadget Lab after the Committee of 300 made attempts on their lives during the events of Shibuya, 2009 and Akihabara, 2010.
  • Hero of Another Story: He is the protagonist of Chaos;Head, and as such had his own conspiracy that he found himself caught up in and had to barely escape with his life during the year of 2009.
  • The Greatest Story Never Told: Takumi ended up saving the world at the end of Chaos;Head, preventing humanity from losing its free will for eternity. However, given that the event was never made public and covered up by the Committee of 300, no one is aware of it. He even laments on Twipo that no one has ever believed him when he tried to spread word of the truth behind the Shibuya quake and New Generation Madness of 2009, everyone believing he was delusional and ignoring his claims that he managed to save the world. Poor dude.
  • Troll: Just like in Chaos;Head, Takumi is still an internet troll who dicks around and messes with people online.
  • He Is All Grown Up: Subverted. Takumi might be an adult now, as this is set 10 years after his last appearance in the Science Adventure series, when he was 17 in the year 2009, but he makes it clear that he still retained his otaku interests and is currently a NEET according to his claims and no current girlfriend, though he does have his own house.
    • Double subverted back into being played straight. It's revealed at the end of the game that he's part of the Anti-Committee resistance that is working to fight against the Committee of 300's plans in the present day, which likely means that a lot of what he says on Twipo is just false information posted to troll the Committee and hide what he's really up to, as he likely is doing it to protect the whereabouts of his friends, who are fellow Gigalomaniacs with the actual power to combat the Committee of 300 effectively. They would likely be in danger if the Committee were to discover their locations, which is likely why he lies about not dating Rimi anymore.
  • Walking Spoiler: Discussing his true identity and what he did in the first game of the Science Adventure series would involve spoiling basically the entire narrative and aftermath of it. In a more literal sense, Neidhardt literally spews out major spoilers for the truth behind the conspiracy of Chaos;Head and his role in the story left and right on Twipo, unfortunately for readers who didn't read the prior entry.

DaSH

An odd twipo user that Kai is introduced to by Sister Centipede in Phase 8. He's actually the right hand man to Okabe from Steins;Gate, Hashida Itaru (DaSH stands for "Daru the Super Hacker"), now 26 years old but still living in Akihabara with a wife and daughter, as well as part of the Anti-Committee group resistance that was formed by the Black Knights and Future Gadget Lab after the Committee of 300 made attempts on their lives during the events of Shibuya, 2009 and Akihabara, 2010.
  • Hero of Another Story: Daru was essentially the best friend character of Steins;Gate, but also played integral role via hacking into SERN and helping to design the phone wave which became the Future Gadget Lab's time machine. He also helped to fix Suzuha's time machine as well, and was Okabe's supporter during their battles in the distant future of Suzuha's timeline.
  • The Greatest Story Never Told: As mentioned above, Daru was integral to resolving the conspiracy during the events of Steins;Gate, however, due to all of the events being undone via time travel to save the world, none of them technically came to pass in the current worldline that Robotics;Notes takes place in. It's heavily implied that Okabe filled in Daru on what happened after the fact though.
  • He Is All Grown Up: Mostly played straight. Daru now has a wife (Yuki Amane) and three year old daughter (Suzuha Amane). He does still retain some of his otaku tendencies though, as shown when he nerds out online with Neidhardt on Twipo.
  • Gondor Calls for Aid: When the Committee's latest plan, Project Mars, is finally put into action and the Black Hole Bomb, Okabe summons the lab mems to arms for a new Operation. Daru states that he's needed for his programming skills in this instance, and he creates a virus that he sends to Sawada, who then sends it to Frau, that allows the Robotics Club to delete Kimijima and stop the Black Hole Bomb from being jettisoned into space, saving the world once more.

KuriGohanAndKamehameha

A composed twipo user that Kai is introduced to by Frau in Phase 9. She's actually the former main heroine of Steins;Gate, Makise Kurisu, now 26 years old and curently residing in America, where she continues to perform experiments and scientific research at Viktor Chondria University.
  • Hero of Another Story: Or heroine in this case. As the main heroine of Steins;Gate, she was integral to the conspiracy of that game, as she was the brains who helped the Future Gadget Lab perfect their time machine, as well as being the reason Okabe accidentally created a stable time loop to begin with that kickstarted the events of the story. Without her help, World War 3 and the shifting of the world onto the Steins Gate worldline never would've come to pass.
  • The Greatest Story Never Told: As mentioned above, Kurisu was integral to resolving the conspiracy during the events of Steins;Gate, however, due to all of the events being undone via time travel to save the world, none of them technically came to pass in the current worldline that Robotics;Notes takes place in. However, it's confirmed in the Steins;Gate epilogue, known as Holy Day of Scourge, that Okabe filled in Kurisu on what happened event wise after the fact though, and she believed him.
  • She Is All Grown Up: While she is a full fledged adult in this day and age, her personality hasn't really changed much from back when she was 18 in Steins;Gate, as she was already fairly mature for her age at the time. She still browses the internet and spouts @channel memes left and right as she did back in 2010 as well.


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