Ep. 1: Yūya reacts to Mitsuki's hospital embrace and subsequent chastity belt ordeal with Hiyori.

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Yūya Kanzaki is startled when his new stepsister Mitsuki collapses and later embraces him as her brother before kicking him out. After resting at home, she discovers a chastity belt on her body. Hiyori, claiming to be an angel, possesses Mitsuki’s body, causing the real Mitsuki to float outside. Hiyori masturbates, forcing Mitsuki back into her body, which triggers an orgasm that partially fills a heart mechanism on the belt. Upset about the device, Mitsuki demands removal instructions. Hiyori explains a button releases the crotch piece for only three minutes, requiring an hour to reset. Interrupted by Mitsuki’s urgent need to use the bathroom, Hiyori leaves her trapped. Mitsuki suffers for an hour, worrying her aunt and Yūya, before finally gaining relief.