共通の趣味を通じて結ばれた「透（ボク）」と「そあ」だったが、透の厳格な父・邦生は二人の交際を快く思っていなかった。ある夜、透の留守中にハプニングが発生し、恐布したそあは図らずも邦生に助けを求める。その際、邦生の逞しさと大人の色気に魅了されたそあは、好奇心から彼を誘惑する。邦生は息子の恋人という事に背徳感を感じためらうも若くエロいカラダに抗えず、二人は一線を越えてしまう・。

"Toru" and "Soa" were brought together by their shared hobby, but Toru's strict father, Kunio, did not approve of their relationship. One night, an incident occurred while Toru was out, and a frightened Soa unexpectedly sought help from Kunio. At that time, Soa was captivated by Kunio's strength and mature charm, and out of curiosity, she seduced him. Kunio felt a sense of guilt about having his son's lover and hesitated, but he could not resist her young and erotic body, and the two crossed the line.