The episode begins with Ryota, Emily, and Celeste talking about the upcoming Harvest Festival. Celeste and Eve set off into the dungeon to gather a large amount of carrots that have appeared in Telulu. Ryota and Emily decide to enjoy the festival and plan to meet up with Alice later.

At the festival, Emily is visibly excited, and they explore various stalls. They come across a strange stall where they receive experience points from a dungeon monster called the flattened mouse. Ryota and Emily decide to try it out so Emily can level up. Ryota uses his reservation spell to ensure Emily both gains experience points and drops an item. They discover a new item called the "Enhancement Shot," which boosts the effect of the next fired projectile.

Suddenly, a monster breaks out of its cage and causes panic among the festival-goers. Ryota and Emily try to subdue it, but it’s not so easy. Neptune and his team from the Neptune Group come to their aid, and together they manage to defeat the monster.

After the incident, Ryota declines Neptune’s offer to join his group, emphasizing his commitment to his own team. The festival continues, and Ryota, Emily, and Celeste participate in an arena competition where they defeat a high-vomiting slime and win a fireworks set as a prize. They enjoy the fireworks, marking a cheerful end to the festival day.

However, Alice senses a mysterious presence calling her from the direction of the Nihonium dungeon. The next day, Ryota learns from Neptune that none of the six dungeons in Secro are producing any drops anymore. Ryota takes it upon himself to investigate the issue.

He heads to the Nihonium dungeon, suspecting the dungeon master might be the cause. When he reaches Floor 4, Ryota encounters the dungeon master but realizes none of his attacks work on him.