Ryota finds himself living alone again for the first time in a while, after his wife returns to her parents' home to give birth. Feeling lonely in the empty house, he's suddenly visited by his sister-in-law, Rena. She greets him warmly and cheerfully, but her true intentions are far from innocent—she's come to seduce him into an affair. Before he realizes it, Ryota is drawn into Rena's irresistible allure. With her beautiful face and sensual body, she slowly breaks down his resistance, tempting him beyond the boundaries of mere familial ties. Their relationship soon evolves into something far more intimate and forbidden...