This is a flashback of when he was younger. In one of the earlier chapters he briefly talks about how he had to eat a lot to bulk up.
huh? i thought that Mokyeon skinny is his current self after Nanjo left him, because in his room there's a picture of Mokyeon and Nanjo from the photobooth on the ground, and that picture is from last season so this has to be a flashforward.
no ur right this is the current time line
OH I MISSED THAT!!
No it's not a flashback. It's the present.
Other than the picture they took together on the floor near his slippers. His hair is long just like it is in the Season 2 poster.
That's the first time I've seen an artist actually make a main character skinny when they're going through their depressive phase. Side characters are always like "you lost so much weight" and then they look the same. It's even more interesting because Mokyeon is the top, and we all know the top must look perfect and buff at all times (though he still has a 6 pack somehow, that's usually the first to go lol). But he actually looks worse, wow