Atsuhiro Sako, alias Mr. Compress, operates as a villain within the League of Villains and its evolution into the Paranormal Liberation Front. Embracing his heritage as the great-great-grandson of Oji Harima, the Peerless Thief—one of Japan's three infamous historical villains—he dedicated himself to crime. His goal: continuing Harima's legacy by stealing from wealthy heroes and redistributing resources to confront societal corruption. Before his villainous turn, he earned a living as a professional entertainer. Tall and slim with pale skin, brown eyes, and a pointed nose, Atsuhiro's signature look involves a black balaclava beneath a white mask displaying geometric designs. His attire includes a dark orange shirt, black waistcoat, dress pants, knee-high white boots, and a brown top hat adorned with a red ribbon and feather. Following the Shie Hassaikai conflict, where he lost his left arm to Overhaul, he utilizes a functional prosthetic supplied by the broker Giran. His personality merges theatrical flair with strategic cunning. Drawing from his magician background, he frequently monologues, employs dramatic gestures, and delights in misdirection—though this showmanship sometimes hinders him, as when taunting allowed the Bakugo Escort Squad to corner him. Despite arrogance, he acts as a grounding voice within the League, mentoring younger members and prioritizing unity. His loyalty manifests in high-risk actions, such as leaping to avenge Magne's murder by Overhaul, an act costing him his arm. He later retaliated by compressing Overhaul's own arm during a prison transport ambush. He resents hero society's imposition of values, advocating for individual choice in morality. His primary ability, the Compress Quirk, allows him to shrink touched objects or living beings into marble-sized spheres. This compression nullifies the target's Quirk and drastically reduces weight for portability. He weaponizes this power creatively: trapping foes, compressing select body parts to maim or kill, repurposing debris (e.g., launching cars with decompressed rocks), and tunneling through solid terrain for infiltration or escape. He can also compress himself for stealthy movement. Post-amputation, his Quirk activation is confined to his right arm. Beyond his Quirk, he demonstrates exceptional agility, speed, and reflexes, enabling him to evade attacks like Shoto Todoroki's ice and traverse hazardous environments like forest canopies. His tactical intellect is consistently noted; he orchestrated the captures of Katsuki Bakugo and Fumikage Tokoyami during the Forest Training Camp Arc, deceived pursuers with decoy marbles, and coordinated complex strategies like freeing allies during the Paranormal Liberation War. His story unfolds across key conflicts. During the Forest Training Camp Arc, he captured Bakugo and Tokoyami but was intercepted by U.A. students during retreat. In the Shie Hassaikai conflict, he lost his arm to Overhaul and subsequently aided in dismantling the Eight Precepts. He participated in the League's merger with the Meta Liberation Army, becoming a Paranormal Liberation Front lieutenant commanding the Brown Regiment. In the Paranormal Liberation War, he sacrificed tissue from his lower back to escape Best Jeanist's restraints, freeing Tomura Shigaraki, Spinner, and Skeptic before defeat by Mirio Togata. Post-war, he was arrested alongside Spinner as one of the League's two surviving members.