That's his JOB. Eak knew that when he entered the relationship. He's not doing it for pleasure, he's doing it because he's good at it and it pays well.
Yeah, probably 90% of the Yaoi population is with ya! LOL! I know I am....I'm too much of a romantic purist, but at least it is made clear he's in love with his innocent demon and the sex is just for work and not pleasure :D
It still sucks that the seme has sex with others will Eak can't do anything about it
I hope they will find a way to make things better