By The Grace Of The Gods Vol. 4

Ryoma Takebayashi is a lonely office worker who lived an uneventful life and died one night in his sleep. In the afterlife, he is met by three gods who decide to reincarnate him into another world filled with fantasy and magic as an 8-year-old boy. There, he’ll learn to make friends, learn and hone his abilities, and, maybe together with a little help from the gods, learn how to live an eventful, happy life.
In Vol. 4, Ryoma is presented with a business opportunity with alchemy that uses knowledge of his previous life. Later, he continues experimenting with his tamed slimes and takes on a demonic beast together with his guildmates.
Notice: This manga is written in Japanese.