Hiwatari, Kai

火渡カイ

Kai is portrayed in the series as a "bad boy." From the moment they meet, Takao and Kai despise one another; Kai's hatred stems from losing a battle in front of Takao and from his perception of Takao as overly picky, annoying, and immature. Takao does not hate Kai, as he simply wishes to be one of Kai's friends, but this proves difficult due to Kai's attitude toward beyblading and life in general. Over time, Kai becomes a member of the BladeBreakers, accepting Rei, Max, Takao, and Kyouju as his partners.
As a natural leader, he leads the Blade Sharks (which he eventually leaves), the BladeBreakers, and the Demolition Boys (Neo-borg). Despite betraying his friends countless times, it appears that Kai's sole desire is power, although his motivations later shift to wanting to defeat only Takao. A difficult childhood and lack of social contact have rendered him completely cold and indifferent to others, though he gradually begins to open up.
For the most part, he is the type of person who remains cool and quiet. This demeanor proves challenging with Takao around, whom he later regards as one of his closest friends. He forms certain friendships with his other team members, but ultimately, his best friend would have to be Takao.