The Dungeon Master manga summary:

'Oh Ju-Yoon' is your typical, everyday part-timer. He dies to a coincidental accident, but because of his kindness, he is given another chance to live in a new and different world. However, his future is neither as a hero, nor mage... but a creature at the bottom of the food chain, 'Brick Worm', meeting an atrocious crisis?! Surreal events! An unexpected level up fantasy!