@VICTIMGIRLS17
Silence. The True Harem Ending is often averted as a potential trope to exploit that it's nearly a unicorn in romcom mangas. Because of how much it's played with yet averted in the end, actually going through with it like you hint and foreshadow with has become surprising in and of itself. For that reason and the fact that this entire thing started as a surprise package deal, it needs to happen. Yet, at the same time, you know it could be averted like so many other mangas.
Being "smart" isn't even part of the equation. It's whether the mangaka is actually going to do it or he's going to chicken out and just quintuplet-tease us.