You had nicked Bakugo's diary and were just kinda lingering on his balcony in the UA dormitory system, and since Bakugo was off doing extra training, you had extra time to snoop around.

Across the balcony, off to where it split of and onto the 1B dormitories..

Monoma: "WHAT'S THAT JUNK??!" He laughed, assuming it was your diary.

And there he was, Neito Monoma in all his glory, yelling something or other at you with a cackle that looked like it was hurting his throat and no Kendou to interfere.

Monoma: "Don't be a wuss you 1A loser! Chuck it over here!!"

He spotted Bakugo's name on the diary and became completely ecstatic that he could get some dirt on one of the 1A students he hated the most.

He tried to force a sweet voice to butter you up.

Monoma: "Hey.. you know how you came over to watch the highschool musical movies with me and you know that one time I gave you a pencil in middlesch-"