The series is centered around high school girl Satō Matsuzaka who befriends a mysterious young girl named Shio, and immediately falls in love with her. She vows to protect that feeling of love, even if it means committing murder.
Shio cares for Satou deeply, but she often remains blissfully unaware of Satou's endeavors aside from Satou's necessary attendance in school and work, as she is not allowed outside of the apartment.
- Main article: Shio Kōbe
