Daimon Kaito (大門カイトDaimon Kaito) is the main protagonist of Phi Brain: Kami no Puzzle. He earns the title of Einstein after solving a "Philosopher's Puzzle".
Kaito has messy black hair that's partly tied into a short ponytail. He has layered dark brown eyes. He is seen wearing sunglasses in his hair and a red unzipped vest over a no-sleeve black shirt. His pants are baggy, green and have two long straps going down to his knees and his shoes are also red with black socks. In later seasons he is seen with a sleeved shirt.
In Season One Kaito seems to be relatively uncaring about things in general, and often does things he knows aren't allowed or he is advised not to do; such as building a maze out of school desks and going to the puzzle club when Nonoha advised him not to because he'll get into a fight. Kaito also is rather blunt, not seen to beat-around-the-bush at any time, speaking his mind. He is a natural Solver who is fond of solving puzzles more than anything else and is able to perceive the feelings of the puzzle creator. If the puzzle challenge is tougher, Kaito will display his concentration, intuition and insight skills.
Kaito is Rook's only friend from childhood and they met while Kaito was a student at the Crossfield Academy in England. Rook was also Kaito's while he was at the Academy as his advanced solving skills (and not being able to understand English) ostracised from his classmates. He first met Rook in the forest where they bonded over puzzles (Rook would make the puzzles and Kaito would solve them) and it is during this time they met Jin Makata, who they both looked up to as a mentor. One day, Rook mysteriously disappears and he doesn't come back for a while. When Kaito see Rook again, they appear to be on good terms but Rook, being the head of the POG in Japan, has ulterios motives. Rook slowly becomes mentally unstable and obsessed with Kaito, influenced by the Orpheus Armband, causing Kaito to do everything in his power to save him and remind him of how puzzles are meant to be fun. When Rook returns in the following seasons, he becomes an important ally and informant to Kaito. Rook treasures his friendship with Kaito and still feels guilty for everything he did to Kaito.
Nonoha is Kaito's childhood best friend and takes care of him by cooking for him and making sure he attends school. She has been with him since before his parents passed away and so, she tends to know what he is thinking most of the time without him saying anything. She has feelings for Kaito but whenever it is pointed out to her, she denies it vehemently. She worries about Kaito and even though she doesn't see the appeal of puzzles, she attempts to learn to solve them so she can help him. Likewise, Kaito is protective of her and does not allow anything to hurt her.
Although it is still uncertain, what kind of feelings he might have for her, Kaito cares a lot about Nonoha, not letting her come in harms way. He even hides the fact that one of her friends, the kindergarten teacher Madoka, is in fact a P.O.G. Giver. Kaito is very outspoken about Nonoha's cooking, calling the "Nonoha sweets" "weapons of mass destruction", which causes Nonoha to punish him physically. As for now, Kaito is the only one who openly dislikes Nonoha's cooking.
Kaito and Rook first meet Jin in a maze while Kaito is studying at Crossfield Academy. Jin helps them out after the two boys get lost. After that, they become attached to Jin after he teaches them about puzzles. People often take advantage Kaito's memories and attachment to Jin for their own gain and this causes many unfortunate incidents to occur. Throughout the first season, Kaito is seen looking for any clues that could lead to Jin's whereabouts. After Kaito finds Jin at the POG Headquarters, he tries to help Jin regain his forgotten memories.
When Kaito first meets Freecell, he does not recognise him and the only clue he is given to Freecell's link to him is a "forgotten promise". While it takes a while for Kaito to figure out why Freecell is so angry at him, he eventually connects the dots. Freecell blames Kaito for his mother's broken heart and eventual death. Despite Freecell's grudge against Kaito, he is shown to genuinely care about Kaito and what he actually wants isn't revenge but for Kaito and him to solve puzzles together for fun. Like Rook, he becomes a trustworthy ally and friend to Kaito in the third season and also like Rook, he is looking for a way to redeem himself for what he did to Kaito.
Initially believing Ana to be a bit strange, Kaito got exasperated and impatient with his laid back attitude and whimsical outlook on life during their first mission together. But after they complete their mission together, he acknowledges that Ana is a talented Solver and he wouldn't have been able to do it without his unique talents. Throughout the series, he gives Kaito advice and a unique persecutive on problems that Kaito has to deal with. He sees Kaito as a precious friend and believes that he has changed for the better because of him.
He is a prodigious solver, being recognised as genius by many other solvers. When he becomes a contractor of the Armband of Orpheus (and uses its powers), his skills are heightened further.
- The eye that Kaito pulled down is the same eye that glows red.
- Daimon Kaito is a pun on mondai kaitou, which means "Problem/Solution" in Japanese.
- He dislikes "Nonoha Sweets" and green onions but he learns to tolerate "Nonoha Sweets" in Season Two.
- "Puzzles don't endanger lives." Kaito (Episode 1)
- "There's no puzzle I can't solve" Kaito to Souji Jikukawa (Episode 1)
- "It's puzzle time!" Kaito (Episode 1)
- "Solved." Kaito (Episode 1)
- "This puzzle wants to be solved." Kaito
- "This is a really nice puzzle but it pisses me off. What pisses me off more is that you are trying to use it for murder." Kaito to Gammon Sakanoue (Episode 20)