Jou is the new member of the Boonboomgers. Ishiro, who is "too serious to trust a police officer who is too serious...", decides to follow Jou to find out what his "secret face" is. Meanwhile, there is a powerful new enemy on Earth.

Taiya reveals his real intentions to form the Boonboomgers, which is to participate in the "Big Bang Grand Prix", the biggest and most important race of the entire universe, while fighting the Hashiriyans was not in his original plans.