Welp, as others have posted, the series has broken the fourth wall and become aware of itself, lol. To me, this foreshadows the near ending of the story, since once again as others have stated, the author seems to be running out/has run out of motivation to continue, and has entered cruise control mode.
I would like to believe all that, but upon closer examination, it's like we're reflecting all the way back to the original conflict: Keita is sexually attracted to his sisters, but won't go all the way with them because they are his sisters. Still, the translation in the middle right panel on page 22 seems a bit weird. Should it have said something more like "No way, that can't be it. Even for me, I think that if it wasn't for the fact that you are my sisters, then...(I'd be fine with it)"? The meaning becomes more clear a couple of pages later, but I was a bit perplexed the first time I read it.