Kai appears in the series as a "bad boy." Takao and Kai hate each other at the very beginning when they meet; Kai hates Takao because he loses the battle in front of him and because he thinks Takao is very picky, annoying and immature. Takao doesn't hate Kai, as he only wants to be one of Kai's friends, but that proves difficult, because of Kai's attitude to beyblading and life in general. With time, Kai became a BladeBreaker accepting Rei, Max, Takao and Kyouju as his partners.
Being a natural leader, he is the leader of the Blade Sharks (which he leaves), BladeBreakers, Demolition Boys (Neo-borg). Betraying his friends countless times, it seems that the only thing that Kai wants is power, though, later, his reasons morph into wanting to beat Takao and only him. Having a hard childhood and no social contact have made him completely cold and indifferent to other people, though he begins to open up little by little.
But mostly, he's the kind of guy that always stays cool and quiet. That proves to be hard with Takao around whom he later sees as one of his closest friends. He develops certain friendships with his other team members, but all in all his best friend would have to be Takao.
