Kazuichi Sōda sports a punk-inspired look: hot pink layered hair often hidden under a gray beanie, sharpened teeth, and thin eyes behind pink prescription contacts. His signature attire includes a yellow-green mechanic jumpsuit with multiple pockets, bright yellow sneakers, and distinctive screw-shaped earrings—a plus sign on the right and a minus sign on the left. At Hope's Peak Academy, he wore a blue jumpsuit and a cap instead of the beanie. As a member of Ultimate Despair, he kept the yellow jumpsuit, added black gloves, and removed the beanie. His personality merges high emotional volatility with mechanical genius. Despite an intimidating exterior, he displays skittishness, cowardice, and frequent panic, often becoming a target of mockery. He lacks a verbal filter, blurting thoughts impulsively and contradicting himself when lying. Trust issues, rooted in a middle school betrayal where a friend framed him for cheating leading to ostracization, prompted his punk aesthetic as a defensive facade. He carries a wrench and feels anxious without tinkering, driven by a passion for machinery—especially vehicles like rockets and bikes—despite suffering severe motion sickness. His romantic interests are shallow and perverse, notably an obsessive fixation on Sonia Nevermind; he idealizes her while dismissing her occult hobbies, exhibiting stalker-like behavior, jealousy of Gundham Tanaka, and an attempted assault on Sonia under the influence of aphrodisiacs. Kazuichi's background involves economic hardship and abuse. His family's failing bike shop left them impoverished. He assisted with repairs from a young age, honing his mechanical skills by disassembling and rebuilding objects. His alcoholic father physically abused him for missing school or failing to sell bikes. Bullied for his unkempt appearance and poverty-related odor, he found solace in auto-shop classrooms. Acceptance into Hope's Peak Academy as the Ultimate Mechanic provided financial relief for his family. There, his talents flourished: he engineered inventions like a 585-mph bike and modified school equipment, though projects sometimes went awry, such as an engine-powered field-line machine rampaging through campus. He bonded with Hajime Hinata, eventually considering him a "soul friend" despite initial distrust. During the Killing School Trip on Jabberwock Island, he repaired critical infrastructure like elevators and crafted "Minimaru"—a miniature robot tribute to Nekomaru Nidai—to comfort Akane Owari. His survival instincts drove schemes to escape, including pedal-powered boats. Kazuichi's transformation into Ultimate Despair was involuntary. Junko Enoshima brainwashed Class 77-B by forcing them to watch Chiaki Nanami's execution via footage laced with mind-altering stimuli. As a Remnant of Despair, he participated in global atrocities, displaying ruthlessness—indiscriminately killing civilians—while retaining his obsession with Sonia. Post-brainwashing, he survived the Neo World Program simulation and awakened from a coma with restored memories. Alongside classmates, he accepted exile on Jabberwock Island to atone. In the Hope Arc, Kazuichi and Class 77-B intervened during the Final Killing Game, overpowering Ryota Mitarai's brainwashed forces to protect the Future Foundation. They voluntarily returned to Jabberwock Island afterward, committing to lifelong isolation as penance. There, he resumed mechanical work, maintaining the island's infrastructure and pursuing his dream of building a rocket ship.