Something that frustrates me with Harem series like these (IE. Mikadono), is the MC eventually stops being a character and turns into a Plot point. They stop being a Focal character and become a Prize and it's always a shame. In the last 10 issues, the MC only said:
"Eat"
"Uhuh"
"Ku ku ku ku" x 2
"You are both Half Breeds"
And he appears only twice in that time for 1-2 panels. And just like with Mikadono, when you focus too much on the girls and ignore the love interest they want so badly, he stops being a character and becomes a prize in a forever ongoing competition
TBF, Master stopped really being a character after the time skip. Except for maybe that one chapter where they took care of another slave girl. That's the last time he really had any impact on the girls outside of making them horny.
Heck, you can even argue before the time skip that he was simply there to act as a moral compass. We don't know about his origins, why he has the respect/finances of a noble, why he wanted to adopt slave lolies, nor why he seems to hold a more liberal view of slaves compared to his assumed peers. Even that necklace he gave to that other slave girl is a mechanic that is never fleshed out.
But hey, I'm not complaining. I wanted to see some horny demi-human incest and it's delivering