Mikami Satoru, a businessman, is stabbed by a criminal on the street and killed. When he regains consciousness in the darkness, he finds that he's been reincarnated as a slime!

The slime Mikami and the Storm Dragon Veldora decide to give each other names. Veldora gives the slime Mikami the name "Rimuru," and Rimuru comes up with a family name for both of them: "Tempest."

After leaving the cave, Rimuru encounters a village of Goblins under attack by a clan of Direwolves. Caught in the heat of the moment, Rimuru agrees to help the Goblins in their battle.

Rimuru and his companions visit the Armed Nation of Dwargon in search of some artisans to help the Goblins learn to supply their own food, shelter, and clothing. However, a skirmish just outside the city gate lands Rimuru and Gobta in a prison cell.

Thanks to Rimuru's skill, Kaijin was able to make and deliver all of the longswords, so they celebrate by going to a bar staffed by elf girls. One of them reads Rimuru's fortune, and sees an image of someone she believes Rimuru is destined to be with.

One day, while working on the improvements to the Goblin Village, Rimuru meets a trio of adventurers and a masked woman named Shizu. Shizu turns out to be the person Rimuru is destined to be with, according to his fortune.