Glad other people see it, Gotou pretty much threw out all his character growth any chance he had with Agawa long term for strange. Really hope this is non canon, it would make no sense they would get together at this point.
You can also kiss that friendship with the gyaru goodbye too, she’d probably hate his guts now.
Yeah that's the one development retcon that annoys me the most.
We had 4 chapters where Gotou legit grew and reaffirmed all he cared for was Agawa, not just sex, and Agawa actually seemed to properly reciprocate his feelings and finally start getting over her inferiority complex with her sister. And now that's all gone for this frankly mediocre threesome and Gotou acting like a horny monkey with no character.
Also, even with this retcon we still have those chapters with the gyaru friend warning Gotou about Agawa's insecurities, so he kinda comes across as a huge jackass now and runs counter to the setup thus far.
I wanted to hope this was just a one-off "what if" but the threesome is already done and the author said they'd rewrite the last 5 chapters so the story is clearly going to follow up from here and not the previous development. I have no idea how the author is going to salvage this, especially with the friend.
My best guess is that in the next chapter or so he's going reaffirm his whole declaration of love for Agawa and that her sister means nothing to him, but that's such a worse execution compared to flat out rejecting the sister's sexual advances, which is what actually impacted Agawa's life and caused her insecurities. The threesome could have possibly worked if Gotou was more insistent on paying attention to Agawa but the sister pretty much always got her way during the threesome itself and Agawa was always grumpy about it, so all that possible development is in the trash.