During their school trip, Katsuki and Shouto encountered a villain in the forest. Katsuki asked Shouto who was supposed to be ahead of them, to which Shouto answered Fumikage and Mezou. Meanwhile, the villain was admiring a severed arm on the ground. However, he realized he had work to do and couldn't afford to be distracted, finally turning his attention to Katsuki and Shouto.
Shouto engaged in combat with the restrained villain (known as Moonfish), using his ice to block the villain’s teeth enlarging Quirk. However, Moonfish proved to be highly skilled, being able to break through the ice and nearly hit Katsuki with one of his teeth, only to be intercepted by his ally's ice. Much to Katsuki's annoyence, Shouto warned him to not use his Explosion Quirk due to the fear of igniting the poisonous gas and causing more chaos.
Meanwhile, Moonfish continued breaking through Shouto’s ice defenses with his teeth enlarging Quirk while also using his teeth to maneuver himself around. The heroes-in-training continue their battle with Moonfish; though Shouto was unable to fight properly due to carrying Kousei, trying his best to keep Moonfish at bay by blocking his path with ice. Katsuki becomes furious that he is unable to fight back as he thought that firing a huge explosion should stop Moonfish, but Shouto warned him that the explosion will limit their visibility and give the villain more attacking opportunities.
When Mezou and Izuku arrive to Katsuki and Shouto's location, Mezou asks one of them to make light, finally letting Katsuki to using his explosions. Before Mezou can explain further, Moonfish sensed Mezou and Izuku’s presence and sent one of his teeth to attack them.
Suddenly, the rampaging Dark Shadow appeared and used its enormous claw to crush Moonfish, destroying Moonfish’s teeth, much to Shouto and Katsuki's suprise. After the rampaging Dark Shadow effortlessly defeated Moonfish, Katsuki and Shouto managed to get close to Fumikage, and used their Quirks in a combined attack of concentrated blast beams of explosions and glacier-like waves of ice to calm down Dark Shadow to make it reduce in size and retracts back into their classmate.
After Katsuki once again told Fumikage that their Quirks have a bad chemistry, Fumikage thanked Katsuki and Shouta or saving him. Izuku told Fumikage that their top priority was to protect Katsuki, who was the target of the villains’.