I don't think they are a couple, the way he cares for the egg boy seems like an older relative, at first i thought about father but i am not sure anymore, an uncle or older cousin fits him more now.
I guess Ashfart is some kind of deity at Emily's realm, that would make Emily one of most powerful people in her world otherwise it's a crazy unbalanced there and most are stronger than Emily and Ashfart.
Do they use different words for "dragon"? Guy was called Dragon God for several chapters but Emily seems surprised he isn't surprised about the dragon.
Technically he isn't OP, his only unique ability so far was talking to anything, besides that all he has is some knowledge helping him to think out of box.
(I forgot about the fight with big guy some chapters ago, that was too much)