By the Grace of the Gods (Manga) 11

Slime's up for one recently deceased middle-aged businessman When the gods reincarnate him in another world as a boy with magical powers, he discovers that magically tamed slime are an untapped natural resource

Ryoma decides to focus on his original job as an adventurer after seeing his laundry business doing well under the care of his diligent employees. Ryoma's long-term goal is to raise his adventurer rank in order to return to his fictional hometown in a dangerous region. After some consultation with the guild, Ryoma takes a job that introduces him to a magic device maker who inspires Ryoma's creative tendencies