Our main character. A lazy member of the Robot Club, he is Akiho's childhood friend who is always seen playing Kill Ballad game which he ranks fifth in the world. His role in the club is Tanegamachine-3's operator and later, the pilot of Gunvarell.
- Catch Phrase: "...but you'll have to beat me in Kill Ballad."
- Cursed With Awesome: He also has "Elephant Mouse Syndrome". 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: Swore to look after Akiho.
- 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.
- 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.
- Lazy Bum: One of his reasons for joining the Robotics Club is so he can freely play Kill Ballad in the clubroom.
- Not So Stoic: He finally shows an emotional outburst to Aki in Episode 19 in order to get her out of her Heroic BSoD. Aki even notes that he's not acting like his usual self.
- Only I Can Kill Him
- Platonic Life-Partners: With Akiho, until their Relationship Upgrade in Episode 21 when they confess to each other.
- Retired Badass: At the end of the series, he uninstalls Kill Ballad.
- 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: He can forcefully activate his ''Elephant Mouse Syndrome.''
- Serious Business: Kill Ballad
- Stepford Snarker: By the second half of the series, he's witnessed some traumatizing events such as Mizuka's death, yet still covers it up with sarcasm. Akiho calls him out on it.
- 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.
- Later, to stop robots rampaging in Tokyo, someone has to beat an extremely difficult round of Kill Ballad.
- Trademark Favorite Food: Eats "Space Candy" when he's ready to get serious.
The President of Tanegashima High's Robot Club which her sister, Misa, founded. Very energetic and optimistic, Akiho's goal is to finish Gunpro-1 project, a project to build a real-life Humongous Mecha 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.
- Braids of Action
- 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, Lamp Shaded by Kaito.
- Clingy Jealous Girl:
- Shows shades of this in episode 5 when Kaito mentions going somewhere with Junna. She at first tells him to have fun, then changes her mind and tells him not to have fun. Later, she gets mad that he'll do whatever the person who beats him in the Gunvarrel game, but not her, and asks if Junna beat him in the game too. She then claims that she doesn't care if he and Junna went on some silly date.
- At the end of episode 14, after Kaito helps Frau to shut down the hacked robots, she starts attending school again. She then puts her arms around his, which causes Akiho to start spazzing out about said new relationship between the two.
- Cloud Cuckoolander: Has shades of this, and sometimes goes off on a tangent about things almost seemingly at random at times.
- Determinator: Though she's not as good as the other members in their specialties, her enthusiasm for building a mecha 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.
- 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.
- Fist Pump
- Genki Girl: Akiho is very energetic and bold, always trying to recruit people in the club. Given the fact that the club has only two members, she isn't very successful.
- Genius Ditz: Prone to do silly things she might be, but Akiho is a good mechanic.
- Hair Style Inertia
- Heroic BSoD: Suffers a minor one in Episode 17 when the Robotics Club is disbanded, and a major one in Episode 19 when Misaki destroys all of the robots at the Expo, including Gun-pro 2.
- Honor Before Reason: 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!"
- Human Humming Bird
- Humble Goal: Wants to finish constructing the Gunvarrel robot her sister started.
- Ill Girl: She suffers from "Elephant Mouse Syndrome" which makes her perceive a few seconds over the course of 5 minutes, leaving her in a comatose state if she overexerts herself. This condition was caused by some kind of accident nine years before the main story starts.
- Justice Will Prevail
- The Leader: A combination of charisma and determination make her the ideal leader of the club
- Letting Her Hair Down: Episode 18.
- Platonic Life-Partners: With Kaito, until their Relationship Upgrade in Episode 21 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.
- Purely Aesthetic Glasses: When she puts her glasses on, expect a Shout-Out.
- Red Oni, Blue Oni: 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.
- Tomboyish Ponytail
- Victorious Childhood Friend
- Wrench Wench: She is often seen wearing mechanic coveralls and actively working on the Gunbuild 1 and 2.
- 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 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 Robot Club.
- Abusive Parents: His dad will get rough with him if he shows signs of going down any career path besides taking over the family fishing business.
- The Comically Serious
- 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: His tilt-glasses schtick.
- 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!
- Large Ham: As Mr. Pleiades, just look at his outfit!◊
- Luminescent Blush: He's actually quite shy about physical contact with girls.
- Meaningful Name: Invoked, Kaito points out that "Subaru" is the Japanese way of saying "Pleiades" the star cluster.
- 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, especially if Kaito isn't around.
- Sempai/Kohai: Since he's actually younger than both Akiho and Kaito (who are in their third year), he always refers to them with -sempai suffix, even when told not to.
- Smart People Wear Glasses / Stoic Spectacles
- 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.
- Sugar-and-Ice Personality
Airi/Geji-nee (Japanese for "Sister Centipede")
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. Geji-nee 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: Geji-nee, oh so very much.
- Grew Beyond Their Programming: Geji-nee turns against Kimijima, unable to bring herself to harm Kaito and the others, though she believes this to be a bug in her programming.
- Hair Antennae
- 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
- Mundane Luxury: More than anything else, Airi wants to see snow.
- Mysterious Waif: Complete with white hair.
- Rapunzel Hair
- Red Oni, Blue Oni: Respectively Airi and Geji-nee.
- Spell My Name with an "S": The dub refers to her as Gezi.
- Split Personality: Kaito can manually invoke this by tapping her forehead. Geji-nee is more straightforward with her explanations than the playful Standard Airi.
- Suddenly Always Knew That: Real Airi somehow has access to Geji-nee and Standard Airi's knowledge of Kimijima's inventions despite not understanding it herself.
- Wetware Body: Real Airi is later possessed by Kimijima's cyber ghost.
- Your Days Are Numbered:
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. Her fear was caused when a robot nearly crushed her as a child. She is also the granddaughter of Fujita.
- Audience Surrogate: Probably the most normal of the cast with no experience with robots.
- Boyish Short Hair
- 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".
- Cry Cute
- Cute Clumsy Girl
- The Ditz
- Face Your Fears: Is determined to overcome her fear of robots.
- I Know Karate
- Imagine Spot: Prone to getting ones about... questionable topics.
- My God, What Have I Done?: A strong wind topples the Gun Pro-2 onto Subaru while she was operating it. He is badly injured and Junna blames herself.
- Purity Personified: Junna is easily flustered by Frau's dirty talk and tends to panic about female decency.
- Shrinking Violet
- Single-Issue Psychology: Had a traumatic experience involving a robot as a child and as a result is terrified of them.
Kona Furugoori (nickname: Frau Koujiro ("Mrs. Koujiro" in German))
Local shut-in and the socially inept creator of Kill Ballad, the wildly popular video game adaptation of 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.
- Anime Hair: Her pigtails defy gravity when they're tied up.
- Catch Phrase: *Something not even remotely sexual happens*"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.
- G.I.R.L.: Kaito initially assumes she was a guy using a female name at first.
- Girlish Pigtails
- 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.
- Leet Speak: Speaks like she is posting to an Imageboard.
- Lovable Sex Maniac: Frau's mind is about as clean as a septic tank.
- Mega Twin Tails: They're bigger than her head.
- Missing Mom: Frau's main motivation for moving to Tanegashima is to search for her mother. It is implied in the Visual Novel that her mother is dead.
- Otaku Surrogate: Specifically for those into the yaoi and moe genres.
- Playful Hacker
- 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 Jun.
- Sore Loser: When it comes to Kill-Ballad, if Frau wins, her opponent was playing fair. If she loses, they were cheating.
- Speech Impediment: Has a heavy stammer that comes out when she's riled up.
- Yaoi Fangirl: She claims to have at least a terabyte of pornographic BL images, and isn't afraid to proposition Subaru for more.
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.
- Aloof Big Brother
- Always Someone Better: Her Catch Phrase. Actually it's Kimijima's
- Brainy Brunette
- 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.
- Cool Big Sis
- I Cannot Self-Terminate
- Fighting from the Inside
- Genki Girl: Comparable to that of Akiho when she was younger.
- Meat Puppet: Kimijima's way of punishing her for stopping his plans.
- Powered Armor: Gets a cybernetic suit that increases her agility and strength.
- Retired Badass: Well, from Robo-One tournaments, anyways.
- Yamato Nadeshiko: When she was in high school.
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.
- Disabled Hottie
- Eat That: Challenges anyone who needs information to buy and eat a revolting cheese/passionfruit-filled, spicy nikuman. Better eat it fast.
- Go Out with a Smile: She asked Kai to thank Misa for the robotic exoskeleton she gave to her as she fell to her death.
- Killed Off for Real
- Knowledge Broker
- Powered Armor: The exoskeleton around her legs help her walk now that she's been paralyzed.
- Secret Keeper: Hid Misaki's murder of Kimijima.
- Team Mom
- 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.
- The Engineer
- Grumpy Old Man
- 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.
- Old Master
- Voiced By: Ayano Yamamoto (Japanese), Brina Palencia (English)
You may know her as the daughter of the 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.
- Expy: An energetic Action Girl who rides her bike everywhere... Looks like Suzuha rubbed off on her.
- 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.
- Reasonable Authority Figure
- She Is All Grown Up: Was only 11 years old in Steins;Gate, now she's 20 and looking good.
- Sixth Ranger: For the Robotics Club.
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.
- Adults Are Useless: Averted, but no one seems to think any better of him regardless.
- Cool Teacher
- 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.
- 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.
- Berserk Button: When two jerks harass and bully Akiho, he manhandles them.
- Eyes Always Shut
- Friend to All Living Things: Sumio apparently has a thing for parrots.
- Gentle Giant: Most of the time.
- Gratuitous English Catch Phrase: "IMPACT!!!"
- Large Ham
- The Team Benefactor
- Uncle Pennybags: Mitsuhiko's uncle, specifically.
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 committee.
- Archnemesis Dad: Will not rest until he has stopped Project Atom and the Committee of 300, which includes his father.
- Badass in a Nice Suit
- 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.
- Skunk Stripe
- Stab the Scorpion: Looks like he's about to pull the trigger on Kai and Aki, he actually shoots at Misaki.
The author of the Kimijima Reports, who died several years ago.
It turns out that he works for the Committee of 300 and caused the Anemone-gou incident which was in fact an experiment that would have killed all the test subjects; This was stopped by Misaki who killed him. However before his death he uploaded his consciousness to the internet and lives on through Iru-o, 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 Geji-nee and Misaki (who was brainwashed by him) do his bidding in the the virtual and real worlds respectively.
- Brain Uploading
- Cybernetics Eat Your Soul: Airi mentioned that he wasn't always obsessed with the experiment and did want to help her, but he lost this when he uploaded to the net and became completely obsessed with the experiment.
- 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.
- Evil All Along
- Non-Action Big Bad
- Only Mostly Dead: Was killed by Misaki. However, he uploaded his consciousness on the net before this happened.
- Walking Spoiler