Death March kara Hajimaru Isekai Kyousoukyoku, Tate no Yuusha no Nariagari Recommendations
Isekai medieval fantasies, that focus a lot more on the actual RPG elements (HP, MP, Skills, etc...) rather than casually ignoring them. Both also feature harems forming due to the MC's heroic efforts
They have the same storyline theme isekai, not only that both of these series have in common that the main characters are called not by a trivial reason they are called to another world to get things done (being heroes), they also take the storyline in the kingdom where slavery is a natural thing.
both Mc are overpowered and they are really kind to slaves and half humans