A bitter conflict turns sour when former student: Kuroke Mutsu attempts to kill his mentor figure: Suzushii Kakomi. After multiple attacks in Tokyo, Japan. Jisei Suzuto agrees to become an Ishiin! Along with tomboyish Manaka Yukinari, secluded Koyo Nayumi, and the battle-hardened Rushiko Hirotsu. They are caught up in the Age-Old Conflict between the Ishiins and the Insurgents.