@BookQueen Rikka and Nanami are fuck buddies. Nanami likes Rikka. Rikka likes Yae. Yae likes Nanami. Rikka confessed to Yae but got rejected. Rikka doesn't know that her fuck buddy likes her like that, and Yae isn't getting any.
I got confused too because I thought it was from the light haired Rikka's POV and not the dark haired Nanami POV. It's an actual love triangle.