For some reason people think any criticism of Nanase means you're defending Yuni cheating, which is ridiculous. I think it's pretty obvious she's in the wrong for that, so it doesn't really need repeating. But I think this chapter perfectly illustrates the problem with Nanase. She's basically treating Yuki like how Yuni wanted to be treated the entire time. She puts her friendship with Yuki above her romantic relationship, and gives her the public affection and time she doesn't give to Yuni.
That's why I question WHY these two got in a relationship in the first place. Like I really need the backstory on what made them get together, because at this stage it seems they aren't compatible at all. Nanase doesn't have her heart in the relationship, yet she's still pissed at the thought of Yuni being taken from her. Yuni is pretty understandable, but Nanase's actions still somewhat confuse me.
Idk wtf is going on with fuuko though, and it'll be interesting to see how she plays into this.