Moonfish/Synopsis

History
Moonfish was a criminal who committed such vile crimes that he was placed on death row. His appeals were denied and so he escaped prison to avoid execution.

Forest Training Camp Arc
Moonfish, Spinner, and Magne meet up with the other members of the Vanguard Action Squad at the Pussycat 's forest reserve on a mountain overlooking the U.A. students training camp. He mumbles about the mission, repeating that he has work to do.

Once the mission to capture Katsuki Bakugo begins, Moonfish stumbles through the forest in search of the target. He happens upon Fumikage Tokoyami and Mezo Shoji, and attacks them with his Quirk. Moonfish manages to sever one of Mezo's Dupli-Arms, but the students get away. Moonfish uses his time to admire the severed appendage. He is eventually confronted by Katsuki and Shoto Todoroki and turns to them while asking them not to distract him from his work.

Katsuki rushes Moonfish, prompting the villain to activate his Quirk. The blades nearly pierce Katsuki, but Shoto blocks them using his own Quirk to build a wall of ice. Katsuki tries to counterattack, but Moonfish's Quirk keeps him at a distance. Shoto tries to freeze Moonfish with an ice attack since the boys can't use their fire-based Quirks while in the forest. Moonfish avoids the attack using his teeth to move between the trees. He suspends himself upside-down in the air and asks his adversaries to show him their flesh.

Moonfish further manipulates his teeth and attacks Shoto's ice walls with the tooth blades. He nearly strikes Shoto, but he evades and continues defending himself with walls of ice. Moonfish stops attacking when he notices Fumikage's gigantic Dark Shadow heading towards him while tearing through the forest. The villain tries to attack Dark Shadow and is instantly crushed by one of its arms. He recovers a few minutes later and angrily tells Dark Shadow not to steal his prize before attacking it again. Dark Shadow makes short work of Moonfish by crushing his teeth in its hand before throwing Moonfish across the forest and incapacitating him.

Some time afterward, Mr. Compress' message concerning the success of their mission is broadcast to all of the members of the Vanguard Action Squad, but the bound villain is slumped up against a broken tree and completely oblivious to his teammate's announcement.

Later, after the rest of the Vanguard Action Squad escapes with the fruit of their labor, leaving the defeated members of their group behind, Moonfish is arrested by the Police Force, still unconscious.

Paranormal Liberation War Arc
Moonfish was in his cell scratching the walls with his retracted teeth when Tomura, controlled by All For One, and an army of Nomus attacked Tartarus and disabled the prison's security system with an EMP attack to free him and every other prisoner. Once he was free, Moonfish immediately used his Quirk to stab and kill any guard and prisoner on sight.