母に連れられて親戚同士の旅行に連れていかれた良和。そこで久々に再会した叔母・凛々子の惜しげも無く晒してくる妖艶な色香に目を奪われて…。すると、温泉で彼の巨根を目にした凛々子は、軽い気持ちで彼を筆下ろすのだった。だが、叔母の手ほどきで性に目覚めた良和は、オナニーを覚えたてのサルの如く、ケダモノと化して凛々子を幾度も犯し尽くしてしまう。だが、凛々子もそれに応えるかのように激しく悶え絶頂を繰り返して…。

Yoshikazu was taken on a family trip by his mother. There, he was captivated by the alluring charm of his aunt Ririko, whom he hadn't seen in a long time, as she shamelessly displayed her body. Then, when Ririko saw his large penis at the hot springs, she casually decided to take his virginity. However, Yoshikazu, whose sexuality was awakened by his aunt's guidance, became like a monkey who had just discovered masturbation, transforming into a beast and repeatedly ravishing Ririko. But Ririko responded in kind, writhing and reaching climax after climax…