Katsuya Serizawa, a powerful esper, spent his adolescence isolated after uncontrollable psychic outbursts caused fear and rejection. Bullied for years, he accidentally harmed his mother at age twelve and confined himself to his room for fifteen years. Toichiro Suzuki recruited him into Claw, providing a psychic-energy-imbued umbrella to manage his anxiety and powers. Serizawa became Claw's strongest Ultimate 5 member, viewing Suzuki as a savior and following orders unquestioningly due to desperation for acceptance and normalcy. During Claw's world domination attempt, Serizawa fought Shigeo Kageyama (Mob). Mob's empathy and shared memories of genuine friendship led Serizawa to realize Suzuki manipulated him. He defected by shielding Reigen Arataka from Suzuki's attack with his umbrella, destroying it. After Suzuki's defeat, Serizawa accepted Reigen's offer to work at Spirits and Such Consultation Office, seeking redemption and societal reintegration. He transformed his appearance by cutting his hair, shaving his facial hair, and adopting business attire. At Spirits and Such, Serizawa assisted with exorcisms and took night classes to compensate for his lack of education. Initial nervousness and dependence on guidance lessened as work and social interactions built his confidence. By the REIGEN spin-off, he was promoted to Deputy Director. He demonstrated protective instincts toward colleagues like Tome Kurata, attempting to remove her curse and dispelling illusions during a rescue mission. He cultivated friendships outside work, declining New Year's Eve drinks with Reigen due to plans with school friends. Serizawa's psychic abilities include high-level telekinesis, energy projection, and forcefield creation, manifesting as a purple aura with TV static patterns. Initially reliant on his umbrella for control—using it as a shield, blunt weapon, or energy conduit—he overcame this dependency. Post-Claw, he channeled psychic energy through business cards for combat and utility, creating barriers or swords. Additional abilities include technopathy (electronic communication), curse removal, and exorcism. He exhibits precision multitasking, such as manipulating objects while conversing. Standing 181 cm (5'11") tall and weighing 72.7 kg (160 lbs), Serizawa has curly dark-brown hair, a broad build, and distinctive eye bags. During his Claw tenure, he wore an orange hanten jacket and constantly carried his umbrella. At Spirits and Such, Reigen groomed him into a professional appearance featuring a blue business suit. He favors gyudon (beef bowl) and calming music, avoids spicy foods due to stomach sensitivity, and enjoys browsing western clothing online. His hobbies include plastic model building and studying, guided by the motto "If I can do it now, I will." Later, Serizawa aided Reigen during ???%'s city-wide rampage but retreated when his powers were drained by the psychic tornado. He participated in resolving the Divine Tree incident and attended Reigen's birthday party, inviting Suzuki's son Sho. His development concluded with independent living and a continued journey toward self-reliance.