This is a story about a girl who wears diapers, and her older brother. One year ago, my father remarried. It was his second marriage, and his new wife had a daughter, who became my stepsister. My stepsister, Kaho, has a complex. Due to her physical condition, she can't hold her urine, so she can't live without diapers. I learned about this not long after we started living together. At that time, she was still a bit distant and called me "Onii-chan" (big brother). "I might be a nuisance from now on..." She confided in me, tears welling up in her eyes. It must have taken a lot of courage for her to do so... I accepted her confession without pity or sympathy. "I don't mind at all. Family is family after all..." I remember her radiant smile at that time. From that day on, I felt like we became true siblings. But what I realized was that the problem wasn't with me, but with Kaho. While it's good that she opened up, the feelings she directed towards me were a bit... no, quite different from those of a normal sibling. In short, my stepsister has a messed-up sense of distance! Even though she's not a little kid anymore, she asks me to change her diaper, insists on sleeping next to me because she sleeps well, and clings to me constantly. Plus, to make matters worse, she's incredibly cute. It's impossible for any brother not to be happy being teased and approached with a smile by such a cute stepsister. At least she could praise me for keeping my sanity. I desperately try to maintain my crumbling sanity while continuing to be a good brother for my adorable stepsister. However, it seems like I'm the only one who thinks that way... This is a new type of diaper drama filmed from a first-person perspective, depicting the daily life of a brother and his lolita-like stepsister.