Dorei Tensei: Sono Dorei, Saikyou no Moto Ouji ni Tsuki - Is Bad.

[alaudae]

Art is good, plot is worthless. The protagonist being a slave has zero impact on the story except maybe a few dialogues. The protagonist can be a friend, a brother, a subordinate, a prostitute, or whatever, and the entire plot can progress just as the same.