The Slime Dungeon (Slime Dungeon Chronicles)

Death came on swift wings. A soul, blessed by a goddess, falls to the land and enters his new life. He clings to a single memory, the defining moment of his previous life. Now, he learns how to succeed in his new life, as a new dungeon heart. To become the best dungeon he can be, he partners with the one existence all dungeons need: his bonded Dungeon Pixie.