Beautiful widow Yuna, having lost her husband, stands with her son Atsushi and her late husband's younger brother, Ginji, as they bow before his memorial portrait. In the quiet solemnity, Ginji secretly makes advances toward Yuna, taking advantage of Atsushi's distraction. The two had once shared a forbidden night of passion. Right before the husband's portrait, Ginji restrains Yuna in her mourning dress, drawing her into a world of taboo pleasure. Though she initially resists, Yuna gradually succumbs to his seduction. Witnessing this, Atsushi—driven by his deep emotional attachment to his stepmother—plots to stop his uncle Ginji's actions. To protect his stepmother, Atsushi finds himself inevitably drawn into conflict with Ginji. This story delves into the complex interplay of familial bonds, desire, sin, and retribution.