Dont you dare put another love triangle in here, i swear to go i will drop this faster than you can say "sakura petals"
I am really on edge here as well...
Major spoilers ahead.
I have a friend who's up to date with the Japanese releases of the manga, and according to him there's not much to be worried about as far as Sumi is concerned. She just likes her as a sister figure, the same will also happen between Yuu and Rina in the coming chapters.
However!
Mitsuki isn't out of the picture yet... expect more from her down the line.
I think there's going to be a Kaede x Yuzu x Rina triangle soon though. That's what's evident from Volume 5 anyway. So Kaede x Yuzu is probably going to happen at some point.
Some evidence of Mitsuki x Rina too.
Well, I know about Mitsuki coming back, and that Rina probably had a thing for her. Just really tired of all the love triangle crap in romance in general. Hopefully it won't happen more than it already has here, or if it does... Ugh. -_-