confused

In his mind now his sunbae isn't serious about him and gave him false hope. So he believes "if I have to give up on my feelings for sunbae, I might as well get something nice out of this and use him as much as he's used me".

Alsoo, he is under the impression that they've already slept together after the dinner they had and he got drunk. So he's being clingy even though he knows his heat cycle will begin soon, out of bitterness probably since his sunbae willingly let him misunderstand.