Responses
I think she sort of figured it out on her own. She did say she saw them in the classroom together. I think she's a hardcore fan of Yuzuriha because it says she is a "pretty face admirer"
She was passing by the classroom when they were fighting (and when they hugged eachother) so she figured out they were dating. Then she talked about it to tokiwa and he confirmed it. Tokiwa didn't tell Yuzuriha about the interaction.
Did the girl already know about their relationship?? And Tokiwa didn't bother to tell Yuzuriha that she already knew?? Is that what happened??