Geez, I subbed thinking it'd be a few bonus chapters. These things are a whole ass manga by itself. Even longer than the main one when all put together.
first 7 are what I expected, some extra chapters that take place in the early days with onee-san. Then next was the Pool arc with the Idol and classmate (and some 3rd girl?) and it's a 16 chapter arc of zaniness. The Idol dedicated route is 23 chapters, and the "Sisters Friend route" (uhh, we never gonna get a name are we lol? They literally titled it "Complicated siblings: Friend Roure ") is 18 chapters. Like, damn.
Hope someone can translate them one day. Didn't realize there'd be so much more, instead of just funny one-offs.