Dungeon no Maou wa Saijaku!?

A boy was entrusted by God to manage a dungeon as the Demon Lord and was granted several divine blessings. However, due to a mistake, he became the weakest Demon Lord in existence. To survive, he must keep creating dungeons. The story involves a foolish main character, a lone demon child, an Undine who resides in a bathtub, and a human princess who falls for the Demon Lord. Events primarily take place during a bath.