Fuyuhiko had a strange habit. When his father was away on a business trip, he would peek into his mother Ayumi's bath. His mother, who actually knew about her son's behavior, called out to Fuyuhiko, who was peeking in as usual, "Let's take a bath together." Fuyuhiko was confused by this sudden turn of events, but from that day on, the bathroom became a forbidden place for the two of them.