Sayonara, Watashitachi ni Yasashikunakatta, Subete no Hitobito

A high school student named Shiori Nakagawa lives in the mountain-encircled town of Akadacho and has been skipping school due to bullying. Mei Sato, a new renter in Shiori's house, reveals to him that she has returned to the town to kill the seven people responsible for the bullying that led to her older sister's suicide. Mei plans to use a ritual at the Akada Shrine to summon the spirit of a snake god into her body. On the summer solstice, the ritual is successful, and Mei and Shiori begin targeting the individuals involved in the bullying. As they carry out their revenge, they grow closer, though Mei keeps a secret from Shiori: the ritual requires her to sacrifice her soul to the god, making her death unavoidable.