Someone said it was a battle to save the world from a cruel fate. Someone said all hope for the future of humankind rested squarely on our shoulders. But I don't care about any of that stuff. That's not why I'm here.
~ Kaito Yashio

Kaito "Kai" Yashio is the main male protagonist of the visual novel and anime series Robotics;Notes. He is the childhood friend of Akiho Senomiya and the only other member of the Robot Research Club at the start of the story. He is an avid fan and skilled player of the mecha fighting game Kill-Ballad, which was based on the in-series anime, Gunvarrel. During their work, however, Kaito accidentally uncovers a global conspiracy that could shape the future of the entire world.

He is voiced by Ryohei Kimura in the Japanese version and Clifford Chapin in the English version, both of whom also voice Kirito Kamui.


Kaito seems to have an affinity for red accents. He is typically seen in his school uniform and wears a red shirt underneath along with a red wrist watch. His eyes are a crimson-brown and his hair is a distinctive red. Kaito's pokecom, which has a red Kill Ballad sticker applied to it, is fastened on his waist.


You'll have to beat me in Kill Ballad.
~ Kai whenever he's asked for a favour
Kaito is best described as lazy, relaxed, blunt and sarcastic- in short, the polar opposite of Akiho. He is easily the more rational of the two and never hesitates to tell Aki the impracticality of her goals. He rarely does anything that requires significant effort and is not even shy about cheating to complete a task if it means he has to work less. Kai is also a very unmotivated person who is easily willing to give up something, in sharp contrast to Aki's unwavering determination, and has little or no faith that he and Aki can complete the GunBuild project before graduating.

Despite being a member of the Robotics Club, Kai has no real interest in robots, and is only a member of the club by request from Misaki, who counted on him to look after Aki after she left. Ironically, he is a big fan of the robot fighting game Kill Ballad and can often be seen playing it, to the point that whenever he is told to do something he doesn't want to or asked for a favour, he tells them they'll have to beat him at it, which due to his skill, almost never happens. However, he nonetheless keeps his word that he'll do what they say if they beat him, which Aki eventually exploits by having him face off against Nae, who is one of the few people who can beat him at the game.

In keeping with his laid-back nature, Kai is generally very calm and level-headed, being able to keep his cool during the entire Robo-One tournament, as opposed to Aki, who freaked out whenever things weren't in their favour. However, he does have a breaking point; he dislikes it when people make fun of Elephant Mouse Syndrome and gets notably angry and annoyed when Frau says it sounds like an anime cliche, since the spasm attacks are extremely painful and he's had to put up with them for most of his life. He can also be quite manipulative at times, as shown when he blackmails Subaru into joining the Robotics Club by threatening to make his secret identity (Mr. Pleiades) public.

Behind his front of aloofness, Kai has been shown to be a kind-hearted individual who cares deeply for his friends, especially Aki, whom he has dedicated much of his time looking after since her sister left. Although he tends to disagree with Aki's decisions, he nonetheless goes out of his way to make her happy, a trait noted by Mizuka. Kai is generally the person Aki turns to when she has trouble making a decision, such as when he convinces her to accept help from JAXA after reminding her what her original goal was- not to finish construction on GunBuild-1, but to create a robot she could show at the Tokyo Expo. He's also the one to get her back on her feet when she contemplates giving up on her dream, though Aki claims that in doing so, he sounds like a completely different person.

Mizuka's sudden demise shakes up Kai badly, to the point that he ends up having nightmares about her, in which she blames him for not doing more to prevent her death. However, he still covers up his trauma with sarcasm, something Aki quickly catches on to and calls him out for. Aki claims that he's always been like this, saying that whenever he feels down, he always hides it behind some joke or sarcastic comment. In general, Kai tends to be a very reserved person, which is perhaps best shown when he catches Aki off-guard with his love confession, and he suspects that he did too good a job at keeping his feelings to himself.

Skills & Abilities

Similar to Akiho, Kaito chronically suffers from Elephant Mouse Syndrome, which he obtained from the mysterious SS Anemone incident. However, Kaito's Elephant Mouse Syndrome causes him to experience a time distortion of perceiving seven seconds to every one second, as opposed to Akiho, who sees five minutes over a few seconds. As a result, when Kaito is under extreme mental or physical stress, he experiences something that he refers to as "Slow-Mo," which he can take advantage of to obtain a kind of temporary super-human reflexes.

After sinking much of his free time into Kill-Ballad, Kaito is an expert at the game. This mastery of Kill-Ballad carries over to his robot operating abilities due to the Robotics Club modeling the robot controls after the Kill-Ballad control pad.


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