Shidara Juri, fearing the cursed sword "Reitei" would be exposed to the world, resolved to seal it away, relinquishing its power. However, Toyokawa, desiring the blade's cursed power for herself, assassinated Juri and stole the sword. Upon learning of the incident, Mizuki, overcome with grief over her brother's death, vows to avenge him. This shock and determination become a crucial turning point driving the story forward.