Voiced by: Yoshino Nanjo (Japanese), Dallas Reid (English)
- "I'm glad you're here for me, RyuZU."
A machine maniac who resides in the Kyoto gear.
- Ambiguously Human: It's never made clear in the anime whether he's really a human kid who somehow pushed his sense of hearing to ridiculous extremes, if he's a relative or reincarnation of the mysterious clocksmith "Y" — or actually Y himself, still around somehow — or if he's some kind of god. One thing is clear — he's certainly not a Muggle.
- Book Dumb: Has little interest in his school studies (aside from keeping his attendance record spotless). However he can build a robot from nothing but spare parts and fixed multiple machines deemed impossible just by listening for the parts that weren't working.
- Brilliant, but Lazy: He is definitely this. He has the unique ability to hear the very gears that make up Ryuzu and their planet, but is content with wasting his time wearing headphones (though given his Super Senses, it's probably to keep him from constantly hearing gears) and lavishing in Ryuzu's attention.
- Crippling Overspecialization: While his excellent sense of hearing allows him to accurately pinpoint problems and count down the total number of gears to the finest detail, it makes him far more sensitive to extremely loud noises than an average human. This causes him to feel dizziness and discomfort when inside mechanical structures and riding cylinder trains, to the point that he sometimes needs RyuZU as a stabilizer to balance out the interfering noises. There's a reason why he wears those noise-cancelling headphones to begin with, and even these don't work in certain situations.
- Cuteness Proximity: It's hard to get him to stop harping on about AnchoR.
- Disguised in Drag: Dons a long-haired wig and skirt when going out and about after the Akihabara broadcast.
- Genius Ditz: Naoto can build one clockwork robot by hand, and repair another one in three hours that Clockwork Masters never could, but seems to have zero interest in anything that is not related to something with gears. To the point he didn't recognize Marie, despite her having been on the cover of a magazine he always buys.
- Headphones Equal Isolation: Played With. While his headphones do kinda keep him from the rest of the world, it's also to keep him from having to constantly listen to the sounds of clockwork.
- Kansai Regional Accent: Being a natural-born Kyoto resident, he breaks into his native dialect a few times when he notices RyuZU, Marie, and Halter transferring into his classroom.
- Ludicrous Precision: When asked how many gears and/or mechanical defects he can hear, he tends to report an exact number, even if there are billions of them, as he did with the gears that make up RyuZU. It's often noted that a normal human could never differentiate that many different sounds even if they could hear them all.
- Mistaken for Gay: When Naoto wanted to inspect Halter's cyborg body and didn't express any overt sexual desire towards her, RyuZU suspected him to be gay, to which he replied that his interest in Halter's powerful and highly sophisticated cyborg body is technical and not (robo-)sexual.
- Non-Action Guy: Justified, as he's more interested in fixing stuff and seeing how machines work. Fortunately his friends and allies can do the heavy lifting for him during fights.
- Older Than They Look: Despite what his stature suggests, he's a high school freshman.
- Actually Invoked by the Army when a bounty was placed on him. They made him out to be even older since a student causing them so much trouble would be humiliating.
- Otaku: For machines.
- Robosexual: It is made quite clearly in Chapter 5 that he has no interest in human women, such as Marie. In fact, after Ryuzu pulls a Time Stop, he asks her to marry him and becomes excited at finding out that Ryuzu has a "little sister" so they could form a family unit together.
- Skewed Priorities: He is motivated to stop the purge on Kyoto so he could save AnchoR, to Marie's annoyance.
- Super Senses: Has Super Hearing, not only is he able to hear a malfunction from far distances, he is even able to pinpoint where it is. He usually wears noise-canceling headphones to block most of it out.
- Took a Level in Badass: In Chapter 2, when he went out of his way to get some creeps to stop harassing RyuZU. Even he was shocked at what he was doing.
- Tsundere: He often argues with Marie but he still cares for her.
- You Gotta Have Blue Hair: Light blue, to be exact.
Voiced by: Ai Kakuma (Japanese), Jeannie Tirado (English)
- "You are a pervert, Master Naoto."
An automaton left behind by "Y". The Unit 1 of the "Initial-Y series".
- Absurdly Sharp Blade: Her scythes are sharp enough to cut through even the toughest metal alloys, and she has no problem reducing state-of-the-art military automata to heaps of scrap metal in seconds.
- Action Girl: Has lots of combat abilities, and utilizes them throughout the series.
- Big Damn Heroes: Stops Hirayama from destroying AnchoR.
- Clingy Jealous Girl: Mostly played for laughs. She gets upset when he gawks at all the machinery after they head to the 24th floor, and wonders if anything with gears gets him this excited. She then states that she's going to strip naked so as to prevent him from looking at other stuff with gears, though he stops her before she can actually do it.
- Compliment Backfire: She seems to be the master at this. She later reveals it is because she was never installed with a Audio Filter.
- Death Is Cheap: While RyuZU can die, being an automaton by nature means that her death isn't really permanent, even after pulling off a Heroic Sacrifice to give Naoto and Marie her Imaginary Gear needed to stop the purge of Kyoto. So just as long as the Imaginary Gear itself isn't destroyed, she can be brought back to life by a few quick repairs.
- Elegant Gothic Lolita: She wears a dark purple old-fashioned-like dress that is laced with frills and ribbons. When she activates her Dual Time Mode, said dress transforms into a Stripperific white wedding dress.
- Gratuitous English: Her supreme command, "Your Slave".
- Hammerspace: Her body is composed of 4,207,600,008,643 gears (four trillion in layman's terms), which itself is an insane number of gears in a small space to begin with, but her body is still spacious enough to fit two large retractable scythes in her.
- Happiness in Slavery: She believes she exists solely to serve the one she sees as her master.
- Lap Pillow: Offers her lap to Naoto as a pillow for him to sleep. He was hesitant at first but accepts and falls asleep. Only to be cut short due to a strong earthquake.
- Lecherous Licking: Sucks Naoto's finger when registering him as her master.
- Luminescent Blush: Is visibly embarrassed when Naoto states that she looks really good in casual clothing.
- Really 700 Years Old: She was constructed one millennium prior to the start of the series by the same super-genius clocksmith who constructed the Clockwork Planet itself.
- Ridiculously Human Robot: Very human-looking on the outside, but actually a superweapon clockwork automaton underneath.
- Sinister Scythe: Has two under her dress on the end of clockwork arms. They come out whenever anyone threatens Naoto.
- Smug Super: Comes across as this due to her audio filter. (Or lack there of)
- Time Stands Still: She can do this with her Imaginary Gear. She's the weakest of all her sisters.
- Tsundere: She cares for Naoto but uses harsh words towards him. While she does care for Marie, she often gets into arguments with her.
- Undying Loyalty: To Naoto. As far as she's concerned, she exists solely for him and everything else in the world is trash.
- Takes the trope to its literal extreme when the gear maintaining her life is necessary to protect him. She kills herself without hesitation. She gets better, being a repairable robot ad all, but how quickly she does it is almost terrifying.
- Violently Protective Girlfriend: God help the poor soul that even talks about doing anything that is even remotely harmful to Naoto's well-being within her hearing range.
Marie Bell Breguet
Voiced by: Saori Onishi (Japanese), Skyler McIntosh (English)
The youngest president of the Breguet company and a first-class clock technician.
- A-Cup Angst: Doesn't appreciate it when Vainney points out that she has an underdeveloped chest.
- Clark Kenting:
- Hers is so bad it makes Clark Kent's glasses disguise a step up. When she fakes her death and becomes an Ordinary High-School Student, she doesn't change her appearance in any way and doesn't hide her prodigy status (which clearly draws a lot of attention). Even one of the students pointed out she looks just like her. The only thing she changes is her name.
- Her only real thing holding the disguise together is everyone's assumption that she's dead. (For the most part, it does seem to be effective and she may also be relying on the fact no one would suspect her to do this.)
- Cute Little Fangs: Occasionally seen sporting one, particularly when she's embarrassed.
- The Determinator: She will do whatever she can to do what's right.
- Going Commando: Lampshaded by Vainney to her embarrassment, when she gets up from bed to talk to him while wearing nothing but her jacket.
- Good Is Not Soft: She is not above threatening the person she is interrogating with death or even the idea of killing the person's family to get them to talk. She would never do it but she puts on a very convincing act.
- Hair of Gold, Heart of Gold: Has the hair part going for her - the "heart" part... depends on her mood.
- Jerk with a Heart of Gold: She often fights with both Ryuzu and Naoto but she does care for them, more so with Naoto. She would never want to see her friends or people she cares about in danger. A very notable example was in episode 6 when she saw both Naoto and Ryuzu seemingly fall to their deaths, she tries to save them but was halted away to safety by Vainney. She then becomes depressed, thinking that she had lost her friends, especially Naoto. When she sees that Ryuzu and Naoto have survived, she kicks Naoto in the face, grabs him and warns him to not make her worried sick about his well-being.
- Modesty Shorts: She wears a pair of dark blue shorts underneath her surprisingly short skirt. Given that she moves around a lot when fighting and repairing stuff, it's very optimal for preserving her dignity while on duty.
- Nice Job Breaking It, Hero!: Marie exposing the purge of Tokyo and causing people to lose faith in the government only made the Army step up their plans.
- Non-Idle Rich: She is the daughter to one of the richest families in the world, and is also the youngest member of the Guild. She is even willing to give it all up without a moment's hesitation to do what is right.
- Ojou: She's president of the Breguet company at 13 years old.
- Ojou Ringlets: She has these, of course.
- Pint-Sized Powerhouse: She's the shortest member of the group, and is strong enough to take down ordinary adult human soldiers with ease.
- Proper Lady: Subverted. Despite her status as president of the Breguet company, she can be one sharp-tongued girl outside of business matters.
- Sweet Tooth: She constantly chews on sweets. It gets more obvious why that is when she's doing repair work: after fixing RyuZU at an astounding pace, she immediately gets an energy crash which she craves for chocolate to cure.
- Tsundere: Type 1. She often bickers with Naoto and has even hit him multiple times, but she still cares for him. Even though she gets into disputes with Ryuzu, she still cares for her. Although unlike with Naoto, she has never hit Ryuzu (not because she doesn't want to, but because Ryuzu would kill her).
Voiced by: Kenichiro Matsuda (Japanese), Christopher Sabat (English)
- Broken Pedestal: Discussed by Halter towards Marie, who states that if a member of the Guild saw her acting like a spoiled princess (which she does in private) they would faint.
- Cool Shades: He wears a pair of sunglasses, which makes him more intimidating and badass up close.
- Cyborg: His body has been augmented with the latest clockwork tech from the Breguet Corporation, which allows him to go toe-to-toe with military automata that would normally pulverize an ordinary human.
- No-Sell: While Halter isn't completely invincible, his cyborg body makes him tough enough to tank blows from regular humans without even flinching. He even lets Marie use his body as a punching bag to vent out her anger and frustration since he can't really be hurt by her.
- Only Sane Man: Frequently comes off as this, notably when compared to Naoto Miura, Ryuzu, and Marie.
- Phenotype Stereotype: Subverted; Halter is American and was a former member of the US Army but doesn't have blonde hair and blue eyes. It helps that he's a cyborg that isn't set to one appearance too.
- Rugged Scar: He has a visible scar on the right side of his face. It's either a battle wound or the result of his augmentation into a cyborg.
- Super Prototype: Halter's cyborg body is the eighth generation model by the Breguet Corporation, which is actually two generations ahead of the current generation of clockwork tech and never really distributed or mass-produced anywhere else. He's the model's first and only user, and naturally, gives him an edge against even up-to-date current gen models.
- Super Strength: Being a cyborg, he's able to smash through a lot of clockwork battlebots with ease.
- Team Dad: Being the oldest member of the group appearance-wise (barring RyuZU) and the only adult, he comes off as this towards both Marie and Naoto outside of his obligation as a bodyguard, and worries about their safety during the most dangerous situations.
Voiced by: Sayaka Senbongi (Japanese), Monica Rial (English)
The fourth in the Initial-Y series automata, and the youngest sister to RyuZU.
- Brainwashed and Crazy: Someone forced a mask on her that makes her act far more violent than she actually is. Her true personality is much more docile and shy.
- Cool Shades: Ryuzu notes that she didn't always have these. Destroying them frees Anchor from the Big Bad's control.
- Hyperspace Arsenal: She can cut open some kind of hole in reality to withdraw a really big sword, a battleship-grade resonance cannon, and at least one alternate outfit.
- Hypno Trinket: The Cool Shades on her face put her under the control of the Big Bad. When they are destroyed, she stops being hostile and becomes Naoto's second servant automaton.
- Lightning Bruiser: Is faster, stronger, and more durable than Ryuzu, able to outpace the older unit even when Time Stands Still. After her HeelFace Turn, she could easily destroy any enemy in Naoto's way, but he absolutely won't let her do that because he doesn't want to traumatize a little girl.
- Person of Mass Destruction: She is called the "one who annihilates" for a reason. However, she's still a little girl mentally, so she's traumatized by the thing she was purpose-built to do.
- Raven Hair, Ivory Skin
- Red Baron: "One who annihilates". A fitting title for a pint-sized Person of Mass Destruction.
- Robo Speak: As an automaton, it's kind of expected, but her constant use of this is one of the signs that she's Brainwashed and Crazy. She stops doing this for the most part when her Hypno Trinket is removed.
- Spike Balls of Doom: Her main form of attack while brainwashed is to enlarge the ball of gears hanging around her neck, set it spinning at high speeds, and then teleport it on top of anything she needs to grind out of existence.
- Third-Person Person: Refers to herself by name.
- Three Laws-Compliant: She cannot target humans for an attack. Naoto exploits this by having Ryuzu stand in front of him — although Ryuzu used Marie for this purpose instead to avoid risking her master's life — and then dodge when Anchor attacks, hitting Anchor with a paralyzing Logic Bomb until the Hypno Trinket on her face could be destroyed. Even after she joins Naoto, she still has to follow any order given to her, even if it's not from him.
- Token Mini-Moe: After returning back to normal and Naoto becoming her master. Naoto heavily dotes on her as his "daughter".
Initial-Y Series Automata
The second in the Initial-Y series automata, and a younger sister of RyuZU.
- The Ghost: She is never actually seen in either the anime, manga, or light novel, merely mentioned in passing by Marie's mentor Konrad as being kept by the royal family of his homeland.
- Amusing Injuries: Averted with her defeat 200 years prior to the series.
- Played straight with her appearances in the manga and light novel, falling off buildings and being hit by a truck immediately after finding Ryuzu.
- Butt-Monkey: In every appearance she's in, she suffers from some form of abuse.
- Cute Clumsy Girl: In designing her, Y took several precautions, most notably designing Tem P without a combat algorithm. This forces her to do all of her calculations herself, and leads to her being unable to utilize her abilities to the fullest. Tem P herself lampshades this, stating that a clumsy girl is cute.
- Becomes a Tearjerker when it is revealed this is the true reason behind why Ryuzu destroyed her and why Tem P continues to try to prove herself to her eldest sister.
- Despair Event Horizon: Ryuzu and Anchor defeat her in combat while the former calls Temp defective. She calls for her master Omega to defend her, only for him to immediately agree with Ryuzu, citing that she is a failure and he has no need for her. Temp is so broken that when Ryuzu issues a Deadly Euphemism and raises her scythes to kill her, she makes no move to escape or fight back, kneeling on the ground to await her fate. It's only due to Anchor's protection that she doesn't get reduced to scrap.
- Dull Eyes of Unhappiness: Gains these where Omega, having seen enough, decides to abandon ownership of her.
- Gale-Force Sound: Her signature ability is control over phonons and resonance. This is taken to the logical extreme as she is able to affect wavelengths of light in addition to sound, allowing her to turn invisible.
- Genki Girl: She is the most energetic of the Initial Y automata seen so far.
- Large Ham: She actually spends hours practicing things like her introduction.
- Leaning on the Fourth Wall: Tem P begins her appearance in the manga by seemingly talking to the reader, but a shot pans out to show she's talking to a stone elephant instead.
- Red Baron: Third of the Initial Y, the Fluttering Butterfly.
- "Take That!" Kiss: She kisses Naoto by the end of the manga and the fourth light novel volume. It's directed towards Ryuzu, who is livid at the action to the point of declaring she would kill Temp, then Naoto, then herself.
The last of the Initial-Y series automata, and Y's greatest unfinished work.
- The Ghost: She has yet to make an appearance. Ryuzu herself doesn't know all the details, but entrusts the project to Naoto and Marie in the final volume of the manga as she believes they have truly surpassed Y.
The person who seems to firmly believe that the Clockwork Planet is not what it appears to be.
- Dies Differently in Adaptation: His death scene was changed in the anime to him dying when the Yatsukahagi explodes instead of being killed by a sniper working for Omega.
- Straw Nihilist: His burning hatred of Y is a result of his belief that he has forced humanity to outlive their destined limits, causing them to stagnate. He maintains that the Clockwork Planet is merely a fantasy created by a god in human form, and has no shortage of speeches on both subjects. After he meets Naoto and becomes convinced that he is Y in disguise, he becomes determined to show Y "the limits of us ordinary people".
- Unwitting Pawn: Is one to Omega.
The mysterious mastermind behind the conspiracies who seems to know more about Naoto and the Clockwork Planet than he lets on.
- Adapted Out: His introduction was cut from the anime.
- It Amused Me: His reason for subjugating Anchor and becoming Temp's master. Ryuzu absolutely detests him for this, and wishes to kill him for playing with her sisters in that way.
- Man Behind the Man: While Gennai is set up as the main antagonist, Omega's entrance reveals that he's been the one behind the scenario the entire time.
- No Name Given: "Omega" is merely a name he made up to hide his true identity.
- Walking Spoiler: Isn't introduced until Gennai's death, which reveals nearly all the events of the first three novels to have been the products of his machinations.
- Xanatos Gambit: Had an answer to every possible ending to his plot. If Gennai's coup had been a success, then Omega would have gained influence as a supporter, and obtained access to the fallen Capital's tower's technology, which he could use to start a war. If it failed, as it did, then he could sell anti-electromagnetic weapons to various eager countries.
The mysterious savior who reconstructed the entire Earth out of gears, and the creator of the Initial-Y series automata.
- Crazy Enough to Work: His idea to rebuild an entire dying planet using nothing but clockwork gears is a pretty crazy one in itself, but he somehow managed to pull it off in the end and gave humanity another chance to thrive once more. It's gotten to the point where his ridiculous feat has been acknowledge and even lampshaded in-universe a couple of times.Naoto: Well - getting the idea to try to make an entire planet function with gears is pretty out there itself, don't you think?
- Crystal Dragon Jesus: In the years that followed since his reconstruction, Y has been praised and even worshiped as humanity's greatest savior to the point that even after a millennium has passed, he is still fondly remembered in history books.
- One-Letter Name: His true name is unknown, and is only ever referred to as just "Y".
- Posthumous Character: He's already (presumed) dead by the time the main story starts since one-thousand years have passed since his reconstruction. The only direct pieces of his legacy that are left behind are his Initial-Y series automata like RyuZU and AnchoR.
- Screw Destiny: His primary motivation for wanting to reconstruct the Earth, as revealed in the prologue of the second novel. He knows full well that the universe, and by extension, the Earth, will eventually succumb to an inevitable heat death, so he decided to challenge that fate as well as current scientific consensus by turning all of it on its head, and converting the base mechanism of the universe into a series of moving parts.