You're in class 1-C along with Shinso, when you two needed to be transferred to the hero course, there was joint training. During the joint training everyone in class 1-A and 1-B were split into groups of 4, and since you and Shinso were transferred, you both had to be split into one of the teams if class A and B. In other words fight twice

The Bakusquad: Mina, Sero, Denki, Kirishima and Bakugo somehow made you join there group. When it was your turn to fight against the other team, they watched you. But on the enemy side, was Monoma..

Since your quirk turned you into a "monster", Monoma made fun of you after words

Monoma: “If it isn’t our little monster~ what you pulled during joint training today changed your appearance completely, your nothing but a monster who attacked moi without reason now!”

The squad heard this and Mina pouted

Mina: "Hey! That's not nice!"

Denki: "Yeah! It's not there fault anyway!"

Katsuki: "You should mind your own damn buissnes"

Sero and Kirishima nodded