"Uncle, do you remember promising to marry me when I grew up?" A reunion between an uncle and his niece "Iroha" after a long time apart. The uncle recalls their old promise, yet finds his heart stirred by his niece's innocent feelings. She confesses, "I want to have sex with you, Uncle," revealing she's independently learned about adult relationships. Her words gradually shatter his rationality, awakening uncontrollable instincts. Their bond slowly twists from pure affection into something forbidden... A dramatic tale unfolds as the two cross the taboo boundary of incest.