Based on the game by Black Lilith.

Igawa Asagi is a veteran Shinobi. After defeating her archenemy a long time ago, she thought she could finally settle down. Yet, her archenemy was revived from death through a pact made with the head demon in the city and swearing to take revenge on her by hurting those who are close to her. Her boyfriend, her sister (also a Shinobi) and she herself are part of the act being abused emotionally and… sexually…