I know many of you will bash me but Mokyeon used to be more handsome and taller than he is...

Now he looks better

He lost so much weight due to poor mental health and as we already saw in previous chapters that he was suffering a lot cuz of nanjo. This is the reason. I love how author portrayed it

I think the depression hit him hard

But while this is understandable,

I do wish Mokyeon adresses his issues the correct way instead of being dependent on Nanjo ,he clearly has unresolved issues from his childhood of abuse and being thrown back and forth and has pretty messed up views on relationship seeing as he automatically assumed his art mentor wanted something from him .

This is very entertaining, but the way to go about this (if we brush past the horrible shit he has done) is not to put himself through Nanjo's mercy (he is simply lucky nanjo is a good person and not taking advantage of his vulnerability) ,but to adress his trauma and how it messed both his mental health and attachement issues .