Goto Imasuji, alias Muscular, possesses a large, bulky frame and short, spiky sandy blond hair, along with tiny black eyes. A prominent scar crosses the left side of his face, costing him his left eye; he carries various prosthetic eye designs in his pocket for replacement. A smaller scar marks his right forehead. Since escaping Tartarus, his hair has grown longer and he sports chin stubble. His typical outfit consists of a black hooded cloak, a white hockey mask pierced with multiple holes, a red tank top, a dark jacket tied around his waist, dark green pants, and black knee-high boots. Muscular exhibits a profoundly sadistic, brutal, and bloodthirsty nature, openly admitting he kills for pleasure. He joined the League of Villains solely to indulge his violent urges, rejecting Stain's ideology. Despite his psychopathy, he holds a personal philosophy: individuals must fulfill their promises or face consequences, defining "right" and "wrong" purely by one's ability to achieve goals. He bore no grudge against the Water Hose heroes for damaging his eye, respecting their honorable fight against him. His overconfidence leads him to underestimate opponents, as shown when he toyed with Izuku Midoriya, allowing distractions to compromise him. He respects formidable foes like Izuku, seeking rematches eagerly, but remains irredeemably committed to violence. His Quirk, Muscle Augmentation, allows him to augment and manipulate muscle fibers, enhancing strength, speed, and durability. He concentrates muscle layers in specific body parts or envelops his entire form in over 12,000 layers for defense. This grants immense physical power, enabling him to shatter rock, overpower Izuku’s early One For All attacks, and survive a 100% Detroit Smash with minimal injury. His speed allows him to outpace exhausted opponents effortlessly. However, prolonged damage depletes his muscle energy, weakening him. During his second fight with Izuku, Grand’s "Tremoring Earth" vibrations unraveled his muscle tendons, leaving him vulnerable to defeat. Muscular killed the hero duo Water Hose during a confrontation, losing his left eye; this cemented his reputation as "The Carnal Murderer." He later participated in the League of Villains' attack on U.A.'s forest training camp, targeting Kota Izumi, the son of Water Hose. There, he fought Izuku Midoriya, dominating him initially while holding back full power. After Kota intervened, Izuku unleashed a 1,000,000% smash, defeating Muscular, leading to his imprisonment in Tartarus. Following the Paranormal Liberation War, All For One and Tomura Shigaraki freed him during the Tartarus raid. Dubbed "Jailbreaker," he led prison breaks across Japan. In one rampage, he attacked Ketsubutsu Academy students Yo Shindo and Tatami Nakagame before Izuku arrived. During their rematch, Izuku employed multiple Quirks from One For All, overwhelming Muscular. Grand’s vibrations further weakened his muscles, enabling Izuku to incapacitate and re-arrest him.