Summer vacation is coming to a close. Wakana received an SOS from Marin, who hadn't finished her homework, so he ended up helping her study at her house. They later realize that Marin had forgotten some math drills at school, so they go to get them. While alone at the school, Marin and Wakana make plans to go to a summer festival together. And when that day finally arrived...

Ryota obtains a second gun, which helps him discover a powerful new use for his special bullets. His exploits catch the eye of Secro's dungeon chief, who has a favor to ask of him...