The Dungeons Demon Lord is the Weakest

Description: God had left a dungeon in the hands of one boy as Demon lord. After receiving multiple blessings from God, lets start my life as the Demon lord!!……was how it was supposed to be, but God messed up and created the worlds weakest demon lord ever. To continue living the new demon lord has to continue making dungeons. This is a story about a bit idiotic protagonist, a lonely demons child, an undine who doesnt live in a lake but in a bathtub, and a princesses who fell in love with the demon lord even though they are human, this is a story that unfolded during a bath.……