When Ryu's father remarried, Erika, who is close to Ryu's age, became his step-sister. The two went on a trip to deepen their sisterly bond, but Erika's interest was in Ryu's body from the beginning. When Erika saw Ryu's body at the hot spring, she could not suppress her desire, and while Ryu was walking outside, she kissed him and demanded his body. Ryu resisted, but she was violated as she was. Ryu still had reservations about same-sex relationships, but he could not suppress his growing feelings and the two of them made love to each other in the guest room at night.