Kaito is a frail boy who hunts slimes on the uppermost level of the city's dungeon. One day, he finds and defeats a glowing slime that leaves behind a very special card, changing Kaito's life forever.

Kaito has achieved great success with his new servant and even dares to venture into the second level. However, it doesn't quite sit well with him that he cannot rely on his own strength.

Kaito has found a new servant card, and this time it's a demoness. Her bold and demanding nature surprises him and seems to meet resistance from Sylphy.

Kaito's now seeing diminishing returns on the experience he's getting from the monsters on floor 3, so he makes the decision to brave the floors beyond... totally unsuspecting of what he's about to find there.

Kaito decides to take part in a dungeon event to get to know some other explorers, but he's going to have a hard time explaining that to his usual party! Meanwhile, on the surface, Haruka works up the nerve to ask Kaito... out shopping?

Kaito tries to convince his servants to let him form a different group. His new partners have big goals as well, and he needs to prepare for them.

Kaito takes Haruka to an open campus event at Ouka Academy, where they meet up with Airi and the rest of her party. Can Kaito manage to take a hint about how Haruka's feelings on the dungeon, much less anything else?

Kaito and the girls take on floor 9 for the first time, where they're in for one nasty surprise after another.