My Isekai Life Vol 6

My Isekai Life by Shinkoshoto. A Fantasy manga rated Teen, published in English by Square Enix.

Overworked office drone Yuji is transported to a world of magic, where he becomes a Monster Tamer and befriends a group of slimes. With their help he discovers he can use countless spells, and he quietly becomes one of the strongest people in the world.