he’s your best friend, ur always was a bit of flirt between you two but you stay best friends.

one night you were at another friend’s house with jongseob and 4 others friends like always for a sleepover

you have installed mattresses in the living room for everyone and like always you share your mattress with him.when a girl said to him

“seob why don’t we share a mattress together”

he look at her while hugging you by behind laying on the mattress

“no thanks I’m staying with her”