Episode 6 of "Akuyaku Reijou Level 99" begins with Yumiella and Patrick staying at school during summer vacation. Yumiella practices controlling her powers using a magic plate designed for level 60 users. She helps other students with their studies and misunderstands their curiosity about her relationship with Patrick.

Yumiella considers how to improve her combat techniques and strategies. She agrees to teach Alicia, who wants to spar with her due to the rarity of light magic. Alicia shares her memories of the starry sky, which helps her understand her magic better.

The episode shifts to the school's martial arts competition, which involves both sword fighting and magic. Yumiella decides to participate after learning that the prize is an amulet that enhances dark magic. She fights her way through the sword combat segment, with several opponents retreating, and ultimately wins by shattering her opponent's sword with a swift strike.

In the magic segment, participants are judged based on their magical abilities. Alicia and Oswald deliver impressive performances. Yumiella, who goes last, uses the powerful spell "Black Hole," unintentionally causing chaos. Despite this, she receives an excessively high score and wins the competition, securing the amulet.

The episode ends with Yumiella reflecting on the value of strength and considering demonstrating the amulet's power to Patrick.