i do not understand whats happening, anyone care to explain??

Ummm.. I don't know how far back you want me to explain but I'll try. So basically, Rika has a pair (as you know) but, it turns out that, Mei actually liked Rika. So he's sad about that and stuff but then it also turns out that Masa and Sougo like Mei. So now it's a love triangle between Sougo, Mei, and Masa (I personally ship Mei and Masa but that's everyone's own opinion) I hope that helped!