Satō Matsuzaka

Birthday: December 31, Blood Type: B, Height: 161 cm

The protagonist of the story. A first-year student at Makisuhara High School. She lives with Shio in apartment "1208." Her parents passed away when she was young, and she used to live with her aunt. She secretly despises her aunt, who showers her with abnormal love, and occasionally feels suffocated when recalling events and statements from her aunt.

She used to engage in promiscuous behavior, unable to understand the feeling of being fulfilled by love. After meeting Shio Kōbe, she learned what love is and became devoted to her. She believes that as long as she doesn't fake her love, anything is permissible, including murder to protect her life with Shio. She describes the happiness she feels with Shio as "sweet" and the unpleasant feelings towards those who harm her as "bitter" or "so bitter it makes her want to vomit." To maintain her life with Shio, she works hard at part-time jobs and saves money by cooking at home. Her experiences with promiscuity and living with her aunt have made her adept at reading people's emotions.

She is beautiful and well-liked by those around her, but to her, everyone except Shio is just a faceless crowd, and she shows no mercy to anyone who gets in her way. She fears losing her happy life with Shio more than anything and becomes extremely agitated when she sees Shio in distress or when she is rejected, nearly driving her to a mental breakdown. However, after killing Shoko in an incident, she plans to flee overseas with Shio, fearing that "everything will eventually be exposed and they'll be separated." Unfortunately, Asahi blocks their escape, and her aunt sets fire to apartment "1208" to destroy evidence, leaving them with no way out. She decides to die with Shio, but just before death, she realizes "true love" and ultimately sacrifices herself to save Shio. After her death, she influences the lives of those she was involved with, and the red ribbon and ring she wore are passed on to Shio.