Engrossed in Bewilderment

Ako and Riko see their parents kissing at the front door, and hear their mother say, "When you come back, you can have all the fun you want." That evening while studying together, Keita, Ako, and Riko, try to block out the sounds of ecstasy coming from their parents' bedroom, and end up in a compromising position in the process. After becoming so aroused by the sounds their parents' (which, as it turns out, they misinterpreted), Ako, Riko, and Keita cannot get to sleep that night, which leads to further intimacy.