TACHIBANA-Mary: Slender's big sister, who was truly lied to by her brother

Takashi, the younger brother of Mary, who had come home from Tokyo for the first time in a long time, was excited because her older sister has become an erotic body. My older sister, who is a little natural and innocent and doesn't know how to suspect people, seems to have never been able to have a boyfriend in Tokyo, so she tells a lie that she has to have sex for a while or she will return to her virginity.