Part of Two Worlds

(Y/N), a new student at U.A, was a first year. Her childhood best friend was Izuku Midoriya. They did everything together, but Izuku always got bullied by others because he was born without a quirk. Katsuki Bakugou, another childhood friend of (Y/N) and Izuku, seemed to bully Izuku as well. One day Izuku disappeared. 2 years later, (Y/N) was now a 3 year hero in training when villains attack the U.S.J, the place the students train. A new villain had joined the League of Villains and is very powerful. She tries to fight them off and protect her fellow peers, but runs into someone very familiar. Who might it be?