Atsuhiro Sako, alias Mr. Compress, operates as a villain within the League of Villains and later the Paranormal Liberation Front. He descends from Oji Harima, the historical "Peerless Thief" who targeted corrupt heroes to aid the oppressed, fueling Atsuhiro's drive to dismantle a hero society he deems unjust and corrupt. His past as a professional entertainer endowed him with expertise in stage magic, escapology, and illusion. Tall and slim with pale skin, Atsuhiro possesses curly brown hair, hazel eyes, and a pointed nose. His distinctive villain costume comprises a black balaclava, a white mask featuring shifting geometric patterns, a brown top hat adorned with a red ribbon and feather, a dark orange shirt, a green-striped bolo tie, a black waistcoat, black dress pants, and knee-high white boots. He initially wielded a silver walking stick with a gold handle. Following the loss of his left arm to Overhaul during the Shie Hassaikai conflict, he utilized a prosthetic from the broker Giran. Later, during the Paranormal Liberation War, employing his Quirk on himself to escape confinement resulted in permanent lower back damage. His personality merges theatrical flair with strategic cunning. Atsuhiro frequently monologues, employs dramatic gestures such as bows after victories, and delights in misdirection, traits rooted in his entertainment career. This showmanship occasionally undermines his effectiveness, like when prolonged taunting allowed adversaries to intercept him during the Forest Training Camp. Despite arrogance, he shows fierce loyalty to the League, acting as a voice of reason and mentor to younger members. His strong camaraderie drove him to immediately avenge Magne's death by attacking Overhaul, costing him his arm, and later retaliating by compressing Overhaul's arm during a prison ambush. He also exhibits pragmatism, prioritizing escape when overwhelmed. His primary power is the Emitter-type Quirk "Compress," enabling him to shrink any object or person within a spherical area around his hand into a small, inert marble upon contact, causing no harm. He selectively deactivates the effect on individual marbles or all simultaneously with a finger snap. The Quirk affects everything within the compression sphere except his own body. After losing his left arm, which partially housed his Quirk factor, activation was limited to his right hand. Tactically, Compress offers versatile applications: instant capture and transport of opponents, exploiting distraction; precise maiming by compressing specific body parts; environmental manipulation using pre-compressed objects like rocks or cars as projectiles or traps; stealth and infiltration through self-compression or tunneling; and misdirection, such as creating decoy marbles during pursuits. Atsuhiro's combat relies on agility, speed, and intellect over raw strength, evading attacks with acrobatic leaps and quickly assessing opponents to retreat when necessary. His strategic acumen includes recognizing diversions and coordinating with allies, like compressing Snatch into Dabi's flames. Key events define his arc: capturing Bakugo and Tokoyami at the Forest Training Camp, using treetop escapes and decoy marbles before being foiled by Aoyama; explaining the League's ideology to Bakugo during the Hideout Raid and being incapacitated by Mt. Lady; losing his left arm to Overhaul while avenging Magne during the Shie Hassaikai Conflict, later compressing Snatch and severing Overhaul's arm in retaliation; sacrificing lower back tissue to escape Best Jeanist and free allies during the Paranormal Liberation War, leading to crippling injury, defeat by Mirio Togata, and arrest. Following the Final War, Atsuhiro remains imprisoned alongside Spinner, the only surviving core members of the original League of Villains.