@KamiKira00
I don't see that as an issue. Feelings can come later. Besides filial love, no relationship starts with people already in love.
from MC perspective, she is stranger
He wrote her. Sure there's a looooot of finer details he doesn't know about her. But he knows everything important about this woman and her relationship with "himself".
Now, of course that relationship she thinks they share but that he knows only partially would be an excellent reason to take some distance from her. After all, the man she married is now dead. It would be respectful to end that relationship officially since it already ended de facto but only one party is aware of it. But then, it seems she despised that dude anyway. In general it seems the mangaka has zero interest in exploring the moral side of the body snatcher element of this story. Seems to be content enough with "that dude was a piece of shit and everybody hated him, the world's much better off with MC in control of his body now". And so I have no expectation that the story will follow that path.
how could it be step forward when girl […] asks you to have closer relationship
Sex. Especially since MC (the author) is still a virgin (I imagine his current body isn't).
Being pervert would regress more his character than advance it.
That's jut your opinion. MC was making sure the content of his pants was still intact 2 minutes into his reincarnation in chapter 1. I don't expect that trait to disappear any time soon.