Mechamaru designates both the mechanical puppets controlled by Kokichi Muta and the identity he assumed while operating them. Kokichi Muta was a second-year student at Kyoto Jujutsu High afflicted by a severe Heavenly Restriction from birth. This condition deprived him of his right arm, rendered his legs non-functional below the knees, and made his skin too sensitive for natural light. Confined within a cave, he survived within a bathtub-like apparatus sustained by medical equipment. In exchange for these physical limitations, he gained vast reserves of cursed energy and the ability to manipulate it over great distances. Unable to physically attend school, Kokichi created humanoid mechanical puppets called Mechamaru as remote-controlled proxies for interaction and mission participation. The standard Mechamaru puppet resembled a robotic teenage male wearing a Kyoto Jujutsu High uniform with a distinctive scarf. Its combat capabilities included firing cursed energy beams from its palms, deploying arm-mounted blades, and using boosters for mobility. Variants like Sword Option, Ultra Spin, and Ultra Shield provided specialized functions. Kokichi harbored deep resentment toward his physical confinement and envied others who moved freely, like the sentient cursed corpse Panda. He longed for a normal life and cherished his connections with classmates, especially Kasumi Miwa, for whom he held romantic feelings. His desperation drove him to form a Binding Vow with Mahito and Pseudo-Geto (Kenjaku), agreeing to leak information in exchange for a healed body, stipulating that Kyoto students remain unharmed. After Mahito healed him using Idle Transfiguration, Kokichi immediately attacked. He deployed Mechamaru puppets as distractions before engaging his Ultimate Mechamaru Mode: Absolute. This colossal armored puppet, piloted from a cockpit in its head, consumed Kokichi's entire lifetime accumulation of cursed energy (17 years, 5 months, 6 days). Its arsenal featured Miracle Cannon energy blasts, Pigeon Viola homing missiles, and New Shadow Style: Simple Domain to counter innate techniques. Though his tactics nearly defeated Mahito, Kokichi was lured into a false victory and killed. Following his death, three pre-prepared Mini-Mechamaru units surfaced during the Shibuya Incident. These small puppets alerted allies to Satoru Gojo's sealing until their power depleted, erasing Kokichi's final presence. A bonus manga illustration later depicted him accidentally holding Miwa's hand in a "lovers' grip". Trivia notes indicate Kokichi named Mechamaru after a favorite anime, preferred strongly flavored food, and had parents who were told he died years before his actual death.