Kamitachi ni Hirowareta Otoko

A middle-aged Japanese businessman named Ryoma Takebayashi dies and is reincarnated as a child in a fantasy world by the will of three gods. He is greeted warmly and chooses to live in the forest, where he practices magic, hunts, and focuses on studying and training various slimes. Some of these slimes are newly discovered. He enjoys a relaxed life in this new world, finding fulfillment in his research and the company of others.