Serizawa has curly dark-brown hair, messy eyebrows and eye bags. He appears to be quite tall, and has broad shoulders and a handsome face.
During his time at Claw, Serizawa had long hair with tight curls, a thin mustache, and stubble. He wore an orange hanten over a black long sleeve shirt, along with grey sweatpants, and bright green crocs. He carried his white umbrella with him at all times. After the fall of Claw, he no longer carries his umbrella casually.
After being invited to work with Arataka Reigen and Shigeo Kageyama at the agency, Reigen trims Serizawa's hair and shaves his face. When working at the agency, he wears a blue two-piece business suit.
Serizawa was a very sheltered and naive person prior to leaving Claw. He placed all his trust in Toichiro Suzuki and looked up to him as a personal savior, and followed his orders without question. Before beginning his work at the Spirits and Such Consultation Office, if he was separated from his umbrella he would panic and completely lose control of his psychic power, which would cause heavy damage to his surroundings. He was haunted by a deep fear of his own power.
Serizawa's constant fear of losing control of his powers made him incredibly anxious. Due to his years under Toichiro Suzuki, he seems to have difficulty acting without guidance from others. However, after the fall of Claw, joining Reigen's agency, and starting to attend night school, Serizawa begins to come out of his shell and be more independent.
Serizawa is shown to be quite caring of others' wellbeing, even going as far as keeping himself in his room for the sake of others' safety. Currently, he is more careful with his feelings and considers his thoughts more before giving advice or commentary. He's gained a little more confidence by working alongside Reigen and making friends with the people in his classes.
At age 12, Serizawa became so overwhelmed by fear of his own psychic powers that he refused to leave his bedroom in fear of hurting others. Lacking guidance and companionship, and not helped by the counselors his mother had hired, he remained in his bedroom for 15 years until Toichiro Suzuki finally coaxed him to leave (and by doing so, join Claw) by offering him an umbrella, and encouraging him to view it as an extension of his room. Serizawa followed him, hoping to learn to control his powers and rejoin society. Instead, Suzuki used him to further the aims of Claw, leaving him and his well-being utterly dependent on both Suzuki and his umbrella. Serizawa convinced himself that Claw was a company, that Suzuki was its president, and that he himself was an employee.
World Domination Arc
When Joseph reveals his status as a double agent to Toichiro Suzuki, Serizawa appears and lectures him about how lying isn't a very nice thing to do. Joseph tries to restrain him with his smoke but he breaks free and uses his powers to blast him out the window.
When Mob is climbing the stairs to confront Suzuki, he encounters Serizawa and tells him bluntly that he was being used. When he tried to argue in his own defense, Mob told him that he was following the wrong person. He made a token attempt to fight Mob, using his umbrella as both a weapon and a shield, but was eventually won over by the sincerity and empathy of Mob's 100% Friendship. By sharing his energy with Serizawa, Mob was also able to share his memories of true friendship with him, which helped Serizawa to understand the true nature of his relationship with Suzuki.
He later used his umbrella to save Reigen from Suzuki's wrath. Suzuki retaliated by blasting Serizawa with psychic energy until his umbrella was torn to shreds, then draining Serizawa's power to use for himself.
Serizawa is present at Toichiro's arrest. His former boss then tells him that he never really viewed him or any of the Ultimate 5 as his comrades, so there was no need to worry about him. Then, in his first show of actual affection and consideration, Toichiro tells Serizawa that people would try to manipulate him because of his lack of self-confidence, and to not let them.
Divine Tree Arc
Serizawa decides to accept Reigen's offer and he start to work at Spirits and Such Consultation Office. After Serizawa is hired at Spirits and Such, he starts to work on improving his life. By helping Reigen with exorcisms, he hopes to help make the world a better place, and he soon starts taking night classes at a local school to make up for his lack of formal education.
Before starting with his first client Reigen decides to cut his hair and shave his beard.
He and Mob exorcise Yokai drawn to the Divine Tree.
Telepathy Club Mini-Arc
Reigen invites Serizawa out for drinks on New Year's Eve, but he already has plans with friends from school.
When ???% is destroying the city, Serizawa and Reigen go check out what is happening and see the tornado. Reigen suspects that Mob is in the middle of it, and asks Serizawa to help escort him to the center. Serizawa agrees and protects Reigen with his umbrella as they walk through it. However, his power begins to be sapped away by Mob's tornado, and at the request of Reigen, he retreats.
In the spinoff, Serizawa is still participating in daily work at Spirits and Such. By this time, he is promoted to the role of Deputy Director of Spirits and Such. He convinces Reigen to allow Tome to come along on some of their exorcisms, and joins Reigen in following Tome on her trip with Origo Hoshida. He then helps with the subsequent rescue by dissipating the illusion of Reigen that was dragging Tome and Hoshida deeper into the woods.
When Tome is cursed, Serizawa immediately tries to remove the curse, but fails and is thrown against a wall, knocking him unconscious.
Serizawa takes part in Reigen's birthday party and invites Sho Suzuki.
Powers & Abilities
When he was a member of Claw, Toichiro Suzuki stated that Serizawa is the most powerful of the Ultimate 5. He is strong enough to block an attack from Suzuki at 3% of his power output as well as to put up a fight against Mob and hold the edge against him for most of their battle. His psychic aura takes on a purple color with a TV static pattern within.
Serizawa possesses extremely powerful psychokinesis, which he channels through his umbrella to make it a powerful weapon both in melee and ranged combat. He can open it to use it as a shield or close it to use it as a powerful bludgeon. He also demonstrated an unnamed technique where he charged a destructive energy ball at the tip of the umbrella and launched it at the opponent. He used the umbrella as a conduit in order to not lose control of his immense power, though he has recently overcome this issue and doesn't require the umbrella to control himself anymore.
- (To Mob) "Please... don't make me angry. Do you know how much your words hurt?"
- "Ability... I can build... plastic models really well. Ah... What else..."
- "How awesome is that... I talked to the prime minister." 
- The name Katsuya means "overcome" (克) (katsu) and "to be, also" (也) (ya).
- Katsuya's surname Serizawa means "celery" (芹) (seri) and "marsh" (沢) (sawa/zawa).
Notes & Trivia
- By the time Serizawa begins working at Spirits & Such, he lives alone.
- Serizawa is reluctant to try spicy foods.
- Serizawa regularly consumes cup noodles.
- Serizawa is shown to be very fond of children - he is friendly toward Sho, the only esper who doesn't want to fight Mob (because he is a middle schooler), and protective of Tome in the REIGEN spinoff manga.
- Serizawa has not told his mother about his terrorist past - she is unaware of what Claw is as well.
- Serizawa considers Reigen to be a respectable person.
- Serizawa is described as being honest and sincere, but too estranged from the world.
- Character Designer Yoshimichi Kameda states that he did not use the umbrella when it was raining.
- When asked about Serizawa's preferences during the summer break, ONE tells that he likes to spend his time indoors, heavily involved in TV, games and the internet.
- During his episode of Salt Middle School Broadcasting Club, Serizawa describes carrying tea leaves, a teapot, and a travel umbrella around with him.
- Serizawa's voice actor Takanori Hoshino imagines him as being blood type AB, a Taurus, and born in April.
|Mob Psycho 100 Characters|
|Main Protagonists||Shigeo "Mob" Kageyama • Reigen Arataka • Dimple • Ritsu Kageyama • Teruki Hanazawa • Sho Suzuki|
|Side Characters||Salt Middle School
Takane Tsubomi • Tome Kurata • Haruto Kijibayashi • Mameta Inukawa • Shirihiko Saruta • Momozo Takenaka • Musashi Goda • Hideki Yamamura • Hiroshi Kumagawa • Jun Sagawa • Ryohei Shimura • Tenga Onigawara • Ichi Mezato • Emi • Shinji Kamuro • Hikaru Tokugawa
|Claw||Boss & Ultimate 5
7th Division Scars
|Evil Spirits & Entities||Keiji Mogami • Psycho Helmet • The Dragger • Wriggle Wriggle • Scent-Ghoul • Boss • Ceiling Crasher • ???%|