Itsuki being the pillar that supports yotsuba should find a way to let yots out of that mindset. Yotsuba won't be going anywhere with that attitude.
On the other note, it would be interesting to see fuutaro's reaction once he learns that lolikano is yotsuba. Would he fall in love again or would his reaction be similar to "i know"?
I still don't get Itsuki, dhe likes Fuutaro too, doesn't she? or is she just trying to help one of her sisters? I think we all can agree, Yotsuba was "childhood friend" candidate since almost the biginning, but Itsuki...