Claire Hasumi, a female investigator who has both the coolness to calmly analyze a situation and the boldness to take action without regard for danger, has earned the utmost trust from the higher-ups. A new mission is assigned to Claire... It is a mission to expose the whole picture of the illegal underground fighting sport <Underground Kate Fight Club>. Claire immediately disguises herself as a fighter and participates in the Kate fight club, getting closer to the bookmaker, but it seems that there is some kind of suspicious connection between her and Emma, ​​the bookmaker...