Tensei Akuma no Saikyou Yuusha Ikusei Keikaku

Kakyu, a former Japanese man reincarnated as a low-ranking devil in Hell, has gained unmatched strength over the course of two thousand years. However, his life takes an unexpected turn when he is exiled to a "different world," escaping the brutal underworld. While enjoying his peaceful, dreamlike existence, Kakyu witnesses the destruction of the village that gave him everything. Despite rushing to the scene, the village is obliterated. Determined to repay the debt, Kakyu rescues the only surviving baby, Alus, and vows to raise him to become the happiest person in the world.