大学受験で叔母夫婦の家に居候する事になった悠斗。久しぶりに逢った叔母・麗香の年を重ねた美しさに思わず見とれてしまうのだが…。ある日、見知らぬ男の声に気付き、こっそり寝室を覗くと、麗香が男に跨っており…！憧れだった叔母の痴態に目が離せない悠斗は、事後の彼女に堪らず迫って…。不貞のスリルと興奮にハマっている麗香は、戸惑いながらも若い男との不倫SEXに幾度も絶頂を覚え、自ら求めて来るのだが…。

Yuto is staying with his aunt and uncle while preparing for his university entrance exams. He is captivated by the beauty of his aunt, Reika, whom he hasn't seen in a long time, but one day he hears a stranger's voice and secretly peeks into the bedroom, only to find Reika straddling a man! Unable to take his eyes off his aunt's lewd behavior, Yuto can't resist approaching her afterward… Reika, addicted to the thrill and excitement of infidelity, is hesitant but experiences multiple orgasms during her adulterous sex with the young man, and eventually begins to crave him herself…