Iroha, a female student who had been living with her mother, gained a sister named Rika around her age due to her mother's remarriage. Iroha felt that Rika, who had lived with her father and had a carefree personality, was someone she could get along with. She also knew that Rika had realized she was a lesbian during her time as a female student and had girlfriends or sexual partners. Rika, who had been secretly targeting Iroha, finally…!
