Callum O'Brien

**Callum O'Brien** (カルム・O・ブリエン *Karumu Ō Burien*) is a major supporting character in the *Jujutsu Kaisen* series. He is a semi-grade 1 jujutsu sorcerer and a member of Tokyo Jujutsu High's faculty, working as the school's Gym Teacher. Originally from the United Kingdom, Callum has been living and studying in Japan since his late teens. He began his career in Jujutsu as a casual, Freelance Assassin and Sorcerer. He enjoyed steady work and freedom before encountering Satoru Gojo, who coerced Callum to come work at the school after promptly "wiping the floor" with him.

## Appearance

Callum is a young man in his early twenties with a lightly tanned, fair skin complexion and sharp features. He has somewhat poor posture, usually being hunched over and is quite short, standing around the same height as Yuji Itadori. He has rather broad shoulders and a slim and lean, yet reasonably muscular physique which he presumably attained through some sort of consistent training regime. His physique however is constantly hidden beneath his usually very baggy clothing, which combined with his hunched over posture and height make him appear rather diminutive and scrawny in stature. He has a very unamusing appearance and often appears to not be paying attention, he sometimes has a gormless look on his face and has a bad habit of letting his tongue flop out of his mouth. He can sometimes be seen with a mischievous and impish smile on his face.

He also wears an orange sweatshirt with black stripes, black pants and sandals.

## Personality

Callum is an easygoing and callous individual who doesn't seem to take anything seriously, often described as having a "bad attitude". He has a pervasive issue with paying attention, losing interest in practically anything if he is not heavily stimulated. He more often than not does not think before speaking or acting. Though he is quite lazy and now spends a lot of his time sleeping, due to his hyperactive imagination and hyper thought process he often struggles to get to sleep, in some instances even going a full day without sleeping. This often results in him being tired most of the time and causing him to drift off in the middle of interacting with people, even whilst standing up.

Despite being a capable combatant, he can be very clumsy, a running gag is that he will trip over objects that are not really in his way and then complain about how said object was in his way. He has a tendency to turn up late even in the most dire of circumstances. As a former assassin and freelancer, money is something that Callum finds himself motivated by, having no real desire to climb the ranks beyond simply getting a larger paycheck. Despite this, he hardly has a taste for the finer things, favouring comfort over practicality or aesthetics and will almost always wear baggy and loose-fitting clothing, often resulting in him being criticised for his poor fashion sense and even one instance, was mistaken for a homeless person.

He likes to read, mostly manga and comic books but he also enjoys expanding his knowledge through research. He dislikes the clichés that surround heroes and finds them to be very boring. Because of this he prefers stories that feature unique character and themes. He also does not like quotes and the heroic and supposedly motivating speeches people commonly throw around as he feels they cheapen and trivialise the ordeal. He himself is very hesitant to say things that fit the typical hero narrative and stereotype and will often call people out for doing said things. He does not seem to care for titles and praise and will often let others take credit for his many accomplishment's without even a second though. He has shown a dislike for people in authority, especially those that abuse their power. He does not like being told what to do, sometimes feeling obliged to do the complete opposite just to be obnoxious and rebellious.

## Abilities and Powers

**Overall Skill Level**: In spite of having very little formal experience and education in the world of Curses, Callum is a highly capable and skilled sorcerer with an interesting and dangerous ability that's intrigued some of Jujutsu Society's higher up's. He is noted by his peers to possess a high amount of potential, but his lazy, lethargic nature and fairly arrogant attitude persist to hold him back. Despite this however, he has managed to gain enough merit to attain the rank of semi-grade 1 fairly quickly. According to Gojo, Cal doesn't use his innate technique all that often, stating it requires quite a bit of concentration. With his innate technique that allows him to become temporarily invulnerable and hide his cursed energy practically instantly, Cal has practically unapparelled potential and capabilities as an assassin.

A further testament to his considerable potential, Mei Mei realised almost instantly that Cal could've killed her if he had tried to at the start of their fight, deeming fighting him without information about his innate technique to be very dangerous. Having gained a real appreciation and fascination with samurai and ninjas, Cal acquired some basic ninja tools, which he treats like collectibles more than weapons, rarely electing to use them in combat.

**Enhanced Strength**: Unbefitting of his average size and slim physique, Callum is superhumanly strong, being able to throw powerful reinforced punches and kicks with enough force to pummel, injure and even break bones. He possesses immense grip strength, he can crush tough materials like wood, stone, bones and even metal with his bare hands. Cal attributes his strength to his own personal regime and the help he received from Mei Mei.

**Immense Speed & Reflexes**: Cal is exceptionally dexterous and quick, he can throw blistering combinations in mere seconds and take some of the most spatially aware opponents by surprise constantly when combing his speed, tactical wit and innate technique. His reflexes are stronger than his physical speed and his eyes can follow the movements of extremely fast opponents, allowing him to activate his innate technique and become intangible in time to avoid practically any form of standard or unorthodox offense.

**Immense Endurance**:

**Enhanced Senses**:

    **Master Hand-to-Hand Combatant**: Much like his innate technique, Cal's fighting style revolves mainly around evasion and counterstriking. He can adapt to combat his opposition seamlessly, using his opponents weaknesses against them, planning several steps ahead of them and using his surroundings all to gain the upper advantage in fights. He has an excellent mind for combat, displaying an exceptionally high fight IQ. He is able to easily physically overpower and defeat a man twice his size and mass and wrestle him to the ground and displayed the ability to disarm someone and break their neck in a wrestle hold.

**Indomitable Will**:

**Great Tactical Intellect**: Despite his layback nature, Cal is capable of being a very keen and perceptive fighter, displaying an unorthodox but still brilliant mind for combat and actually being considered something of a "unique" genius by Gojo. He is knowledgeable of the abilities of a great many sorcerers and is generally quick to gather intel on Cursed Spirits he comes into contact with, showing cunning in order to prepare counter strategies. Even mid-fight, he retains a sophisticated degree of analytical prowess, allowing him to read an opponent's movements, predict what they are going to do, and decide the most effective countermeasure. Otherwise, Cal seems to possess relatively average-level intelligence, especially in the fields of mathematics, science, and world history. Although he was at best a painfully average student, he has displayed an excellent understanding of the human body as well as its capabilities, specifically in relation to the science of what the human body is capable of. He has shown the ability to articulate himself in quite an intelligent and articulate manner when he wants to, often stunning those around him that have to expect incompetence and a thick-headed disposition.

### Jujutsu

**Great Cursed Energy**: Callum possesses a notable amount of cursed energy, being capable of using his innate technique countless times over the course of a day without much effort. He can utilize his innate technique while reinforcing his body with cursed energy for a considerable period of time without showing any signs of running low. Cal's cursed energy also possesses an interesting quality. Cal boasts the capacity for immense cursed energy output, allowing him to reinforce his body with cursed energy to amplify his physical abilities. He can also enhance the physical attributes of weapons and even inanimate, everyday objects, turning even something as mundane as a pencil into a weapon with sufficient penetrative power to pierce a human body.

**Limbo** (ボン, *Rinbo*?): Callum's innate technique grants him the ability to enter a separate dimension. Cal describes this technique as the "ability to interact with another dimension". His main usage of this technique is entering this separate dimension so that he appear as though he can phase his body through physical matter in the real world. He can choose to make one part of himself intangible or his entire body. He is also capable of affecting inorganic matter (such as weapon's and clothes) with his technique and even sentient life, though he can only do so with Cursed Spirits at this point in time. This allows him to smoothly maneuver through solid objects and effortlessly evade incoming attacks. He can turn different parts of his body intangible, specific steps need to be taken for him to move through walls and surfaces without him falling through the floor, with each step requiring great concentration. He can intentionally entangle people or objects within walls, or cause harm by making their hand solid inside a person's body, which could lead to the victims death. Powerful electricity and electrical currents can bridge the molecules in phasing, potentially harming him even while insubstantial. possesses the ability to pass through solid matter and objects by passing her atoms through the spaces between the atoms of the object through which she is moving. When he is phasing, she is, for all intents and purposes, intangible. Hence, when attacked, she can shift into a "phasing" state, even if she is not at the time passing through an object, so as to allow oncoming projectiles or attacks to pass through him harmlessly, rendering him virtually untouchable. Cal passes through objects at the same rate of speed at which he was moving before he "entered" them.

## Equipment

Having gained a real appreciation and fascination with samurai and ninjas, Cal acquired some basic ninja tools, which he treats like collectibles more than weapons, rarely electing to use them in combat.
**Kunai**:

## Relationships

**Jujutsu High**

* **Satoru Gojo**: Like most sorcerers, Cal respects Gojo a great deal and to some extent fears him. He does often find him to be a combination of amusing and annoying and constantly rejects the former's attempts to tutor him. He doesn't seem to hold any animosity towards Gojo for defeating him, though when the latter pokes fun at him for losing, he expresses some irritation at being reminded. Gojo serves as a good point of refrence for Cal, representing the peak of jujutsu. Even though he doesn't believe he can ever beat Gojo, he still seems keen to try.

* **Shoko Ieiri**: As far as fellow teachers and colleagues go, Shoko is the closest thing Cal has to an actual friend. He finds her smoking habit to be a touchy subject but elects to tease her about other things and he thinks that despite her "emo" attitude, she's a massive softy at heart, something she vehemently denies. Shoko has shown that she is fond of him but she also seems to distrust him a little bit, viewing him as extremely unpredictable, having a hard time figuring out what kind of person he is, and never knowing what he is thinking.

* **Megumi Fushiguro**: Cal seems to think of Megumi the least favourably of the first years. He thinks he's too serious and is too scared to let loose. This being said he thinks he's a kind-hearted person at heart.

* **Nobara Kugisaki**: He reprimands her for her lack of physical prowess, singling her out as the physically most lacking first year.

* **Yuji Itadori**: While Cal views Itadori in a mostly positive light because of his compassion, strength, and willpower, but he also looks at him as being a highly naïve and idiotic "kid". He

* **Maki Zenin**: Cal has a great deal of respect for Maki, particularly for her tenacity and physical prowess, however, he recognizes that she'll never become truly to the next level unless she finds a way to "evolve".

**Jujutsu Sorcerer's**

* **Kento Nanami**: Nanami is one of the few professionals that Callum has met that he doesn't immediately dislike, finding his dry wit, candor and views on life and work to be quite pleasant and refreshing. Nanami makes no effort to push Cal into doing more work or training more, something the latter appreciates a great deal.

* **Mei Mei**: Cal has been warned by numerous people (including Gojo) that Mei Mei is a "dangerous" woman in multiple ways and he shouldn't take her lightly. He finds her to be incredibly frustrating, he doesn't believe that she really respects him, he feels like she treats him like a nuisance or an annoying kid. Despite having a notable appreciation for money, he admittedly finds Mei's borderline obsession with it to be somewhat disturbing or concerning. Though he does not find her focus on wealth to be something significant enough for him to comment on, this can not be said for her "creepy" relationship with her younger brother, Ui Ui. Mei recognizes Cal's potential, both as a sorcerer and as a source of income for herself to benefit from. Cal does respect her a great deal, in part due to her strength but also due to her unapologetically miserly nature. He came to learn quite about about Jujutsu from her and her experience with physical training helped him develop his skills outside of his innate technique.

* **Ui Ui**: Cal does not get along particularly well with Ui Ui, the former instantly dislking him due to his close proximity and familiar tone with Mei Mei. Ui Ui seems to recognize Cal's talent as a Sorcerer (in large part to Mei Mei's positive reception) but even so, he remains adamant that Cal is undeserving of working alongside his beloved older sister. Ui Ui was also willing to teleport Cal to England, though this was only after being told to do so by his sister.

**Enemies**

* **Sukuna**: Like other special grade cursed spirits, Sukana is Cal's sworn enemy. He naturally wishes to destroy the ancient Cursed Spirit and does truly believe that he is too dangerous to be left alive.

* **Kenjaku**:

**Non-Sorcerer's**

* **Benihime**:     Cal has a very close relationship with one of his former PT clients, who has essentially become his only real friend in Japan. He thinks very highly of her and she thinks she's the sweetest person he's ever met.

## Battles & Events

****Chapter 0****

* Callum O'Brien vs. Satoru Gojo - Loss

****Fearsome Womb Arc****

* vs.

****Vs. Mahito Arc****

* vs.

****Kyoto Goodwill Event Arc****

* vs.

****Death Painting Arc****

* vs.

****Shibuya Incident Arc****

* The Shibuya Incident
* vs.

****Itadori's Extermination Arc****

* vs.

****Perfect Preparation Arc****

* vs.

****Tokyo No. 1 Colony Arc****

* vs.

## Trivia

* According to the Jujutsu Kaisen Official Fanbook:
	+ His hobbies are watching movies, playing video games, reading manga, sleeping and writing.
	+ Favorite food: Chicken fajitas or teak and potatoes.
	+ Least favorite food: Most seafood.
	+ Cause of stress: Money and relationship problems.