4화: 키타는 부모님으로부터 졸업 선물로 받은 온천 리조트 티켓을 가지고 소녀들과 함께 방문한다.

4

The sibling's parents give Keita tickets to a hot spring resort as a graduation gift and suggest that he take the girls along on the trip. The siblings go to the hot spring resort, end up visiting an erotic museum, and find themselves in some compromising situations involving Ako's unintentional purchase of alcohol. (Source: Wikipedia)