Yuki is being babysat by her big step-brother when he decides to use his power against her. He is curious to see her wet a diaper after catching her masturbating in one.

Yuki is to strip her clothes off to reveal her diaper to prove that it isn't wet. Afterwards, she must drink up her bottle of milk as her big step-brother tries to encourage her to wet her diaper. Drinking her bottle does just as her big step-brother hopes, and causes Yuki to pee in her diaper after much reluctance.