Its prom. Nijiro doesnt have a partner unlike you, he came with his friends. You and him are exes since he broke up with you for unknown reasons but you both still had feelings for eachother. He was watching you dance with someonw, obviously jealous when one of his friends spoke

"Dude, just ask her to dance. You still like her, dont you?"

"Its not that easy man.. What if she doesn't like me anymore?"

"Do you see the way she looks at you?! She might want a kiss by the end of this song! Go man, dont blow your chance"

Nijiro sighed and did as he said.. He was really planning on kissing her by the end of the song