A battle junkie gets reincarnated into a world of monsters and magic by the reincarnation god. In exchange for his memories, he is able to gain OP level skills along with an ability to summon the reincarnation god.
It would be a decent manga if it stopped pandering to fan service scenes. The author just doesn't know how to do them right or in a tasteful way and it obstructs other parts of the story that could use some polish.
Kuro no Shoukanshi