仕事で父が参加できなくなった親戚同士の温泉旅行に代わって行くことになった良和。妖艶な肢体を見せつけるように挑発してくる叔母・ゆなとの再会は、若い彼にとって刺激的過ぎて…。昂る性欲を鎮めようと風呂でこっそり自慰に耽ってると、そこへゆなが訪れる。ギンギンに肉棒を滾らせた彼に堪らず欲情してしまった彼女は、いきなりしゃぶり始めて…。幾度も射精を促され、性の悦びを知ってしまった良和は、サルのように彼女を犯した。そして夫だけで物足りない日々を送っていたゆなも夢中で彼を求めて…。

Yoshikazu is asked to take his father's place on a family hot spring trip because his father can't go due to work. His reunion with his aunt Yuna, who provocatively flaunts her alluring body, is too stimulating for the young man… Trying to calm his rising sexual desire, he secretly masturbates in the bath when Yuna comes in. Unable to resist her desire for his rock-hard penis, she suddenly starts sucking him… After being made to ejaculate many times, Yoshikazu, having discovered the pleasure of sex, ravishes her like a monkey. And Yuna, who had been unsatisfied with her life with just her husband, also craves him…