Look, I don't condone cheating. However, Yuni is in between two women where one is sole purpose is volleyball and the other is to manipulate. Yuni has rejected Fuuko multiple times but Fuuko did not stop. Nanase wasn't there when Yuni was wavering. Yuni is an unstable high school kid who needed an anchor to stay afloat. That anchor never held on to her, but rather a buoy leading her to a different path. Everyone is guilty here.