Tatsumi leads an ordinary life attending school and living with his strict older brother who has taken on the role of both mother and father since their parents passed away when they were young. One day, Tatsumi and his friends attempt to rescue a woman from abusers but are unable to defeat her in combat. The woman then addresses Tatsumi by the name "Rui," leaving him perplexed as to her identity and intentions. Furthermore, Tatsumi must unravel the mysteries of why he is being targeted by strangers and why his brother's behavior has undergone a significant change.
