Two unmarried workers at a travel agency hear about a branch office being opened in a distant land to be staffed by single workers, so they decide to marry each other to avoid that fate.

In this spinoff series, Rimuru gets his hands on a notebook and decides to compose a record of his many adventures. But where to begin?

Bell Cranell is a rookie adventurer and the sole member of his dirt-poor guild founded by the petite goddess Hestia. Adventurers come from far and wide looking to strike it big in the massive labyrinth known as Dungeon, located beneath the city of Orario. Bell is more interested in picking up girls than Dungeon-crawling, but his reality check comes sooner than expected. Saved from a brush with death by the beautiful, renowned adventurer Aiz Wallenstein, Bell falls head-over-heels and sets his sights on winning her heart, but she's not the only woman he's caught the attention of, for better of worse.