Kai Amataro

1="Jundou."

- Hell Bro's's Transformation phrase

2="Just as I thought... Who would have thought has been stymied by not just Kamen Riders, but with the help of these " "You... You're with, aren't you?!" "What of it?" "Where is What did you do to my partner?" "I have no idea who is this Speedor you're talking about. And I forgot when was the last time we went into the."

- Kai being confronted by for the first time.

3="I suggest you people stay away from Foundation X's affairs. The next time I see you interfering with our grand plan, I will show no mercy to any of you. Have a nice day."

- Kai giving a warning to the Kamen Riders and Go-Ongers



Kai Amataro (天太郎 解) is a member of  and the main antagonist of Engine Sentai Go-Onger: 10 YEARS PRELUDE feat. Kamen Rider Build.

History
TBA

Personality
"Abandon your, give up on the who left you. Feel no guilt for leaving your friends in the other world behind. If one of you could find the will to be ruthless, then you'd be freed from all your stress in an instant."

- Kai convincing the Go-Ongers to give up searching for their partners and their former teammate.

Kai is a cold and arrogant man, but also completely heartless and callous at the same time. Though he keeps the guise of a polite and professional researcher, Kai, like most known members of Foundation X, is devoid of emotion and empathy. However, he is quick to draw the line on people who commit even more heinous acts, such as history of child abuse leading him to cut ties with, and the  working for the Foundation was labeled a traitor for his role of the incident caused by him and.

Despite these moral boundaries, in reality, Kai lacks any sense of morals, only serving as a mask to his true personality; he is a callous, deceptive, manipulative, and misogynistic sociopath whose motivation is his God complex. To him, he views friendship and even the bond between humans and Engines as an alien concept. His arrogance and heartlessness is so great that Shinobu Katsuragi is very distrustful towards him and he is even disturbed by his personality, and he is even the first human villain to ever test each of the Go-Ongers' sense of justice.

Portrayal
Kai is portrayed by Hirano Shō (平野 紫耀). As Hell Bro's, his suit actor is Imai Yasuhiko (今井 靖彦)

Etymology
His surname means "the eldest son of the heavens". While his given name translates to "solution".