Everyone getting mad he didn't shag her seems to be overlooking a few things.
Firstly that she quite openly wants his power, not him. Why chain yourself down/ give her levarage over you like that just for some action? If he just wanted sex he has that servent girl whom would no doubt comply. Hell, I dont doubt the cat or elf might aquiest to it too.
Secondly his social anxiaties make anything short of his Abrasive demonlord RP remarkably difficult. This falls within the bounds of something not covered by that. Lets not forget how hard he finds it to be directly nice to his comrades inspite of everything and has to slather it with pretence.
Thirdly it's ecchi tagged, not smut. You want an isakai where the mc sleeps around, try that tag instead.