This is such an interesting dynamic. MC really thought he could pace their relationship like normal but against Yako? Good thing teach was there to kick him into action.
I think MC's motives are very understandable, he's trying to salvage anything he can out of his situation for survival but he's still genuinely trying to not hurt anyone if possible. He recognizes that Yako is a kind person despite her quirks and is willing to try to give her what she needs, someone who truly loves her. Even if he couldn't do it at least Yako seems to be enjoying the time she's spending with him, at worst they could work out a compromise as good friends instead. (but you know that's not gonna happen this is a romcom after all bro would be head over heels for her before he realizes it LOL)
My question is why did whoever arranged this marriage for money not tell her at all about it? Did they really just take one look at this child and went "It's so over, let's just pay someone to marry her"