"How did a girl get on an all boy volleyball team?" "I don't know!"

Kozume Y/N moves to miyagi to attend Aoba Johsai where she meets Oikawa Tooru who doesn't know she is girlfriend of Ushijima Wakatoshi. When he ends up knowing it, he starts mistreating Y/N because of his rivalry . What if life has other plans? What if he falls for his rival's girlfriend??