Ui Ui

Ui Ui is a supporting character in the Jujutsu Kaisen series. He is a sorcerer and the younger brother of Mei Mei.

Appearance
Ui Ui is a young boy with a small slender frame. He has light blue hair, styled with a neat left-sided part and thin eyebrows. Ui Ui wears a long-sleeved jacket similar to the Jujutsu High uniform. He also sports suspenders, shorts, long socks, and simple shoes.

Personality
Ui Ui is a mature and proper young man who really doesn't display any typical traits for someone his age. He's defined by his loyalty and devotion to his sister. He worships Mei Mei and is more than happy to do all of her biddings, even willing to die for her. Ui Ui expresses great disdain toward any individuals who inconvenience or disrespect Mei Mei in any way. He wasn't very friendly with Yuji while they were on the same team in Shibuya simply because he was too close to Mei Mei. Ui Ui is horrified whenever Mei Mei gets in danger but this quickly changes to excitement when she turns things around.

Shibuya Incident Arc
On October 31, Ui Ui is with his sister and Yuji Itadori at Aoyama Cemetery while Satoru Gojo handles the problem in Shibuya. When Mei Mei gets a call about a certain appearing at Meiji-Jingumae Station, Ui Ui along with Mei Mei and Yuji head out to check up on it. Once they arrive at Meiji-Jingumae Station, they are informed about situation that is happening at the station. After being informed, Ui Ui and Yuji wait by an entrance while Mei Mei uses her power to spy on what is happening in the station. When Yuji gets impatient, Ui Ui tells Yuji to calm down while his sister is checking out the station. Once Mei Mei is finished with her task, he listens as Mei Mei explains everything that is happening in the station. After listening to this, Ui Ui heads out with his sister while Yuji enters the station through a different entrance. When the curtain has been raised, Ui Ui informs his sister. The two then heads to B5F platform to wait for Yuji.

Once Yuji arrives at their location, the three head off to were the trapped people are at which Ui Ui carries his sisters axe along the way. While running, Ui Ui gets angry at Yuji for not accepting his sister compliment. Once they arrive at the station, they notice that only one person is there. Ui Ui, along with Mei Mei and Yuji, then head towards Gojo's location, but stop when Yuji is suddenly contacted by Kokichi Muta. Ui Ui listens along with Mei Mei and Yuji, as Kokichi what had happened to him and the situation that is happening in Shibuya. After Kokichi explains everything to them, Ui Ui decides to help his sister face off against the curse users while Yuji heads back to help Gojo.

Once the curse users get close enough, Ui Ui prepares to fight them along with Mei Mei and Yuji. After the curse user's cursed spirit is defeated, Ui Ui watches as his sister defeats him as well. When Mei Mei defeats the other cursed users, Ui Ui informs his sister that the curtain has come down and the two head towards the station. After a while, Ui Ui and Mei Mei are confronted by Pseudo-Geto. Ui Ui then watches as Mei Mei deals with the cursed spirit that Geto had left them. When Mei Mei manages to figure out how Smallpox Deity's attack works, she asks Ui Ui to die for her which he agrees to. As Ui Ui raises his cursed energy to its max, Smallpox Deity seals Ui Ui in a coffin. Smallpox Deity tries to use his attack on Ui Ui, but is doesn't work since Ui Ui used simple domain to block the effects of Smallpox Deity's ability. Once Smallpox Deity is exorcised, Ui Ui and Mei Mei are released from the spirit's domain. Ui Ui and Mei Mei then prepare to face Geto.

Ui Ui and Mei Mei are seen in a hotel room in Kuala Lumpur, Malaysia, having escaped Geto off-panel using Ui Ui's cursed technique. While there, Mei Mei calls an associate and asks them to sell off all of her Japanese assets, in view of the events that have unfolded.

Current Arc
During the Culling Game, Ui Ui became affiliated with the group of sorcerers, and was used as the means of communication by group members.

Abilities and Powers
Overall Skill: Ui Ui is still too young to be a professional jujutsu sorcerer. However, he's still capable of handling dangerous situations and being a useful asset in battle. Mei Mei trusted him on her team during the Shibuya Incident with Yuji. He carried her axe outside of combat and was responsible for countering domains, making him useful to his grade 1 sister rather than a liability. Regardless of his age, Ui Ui possesses a talent for jujutsu, proven by his ability to use his innate technique as well as barrier techniques.

Trivia

 * "Ui" when written as 「憂い」 means "unhappy, sad, gloomy".
 * According to Jujutsu Kaisen Official Fanbook:
 * His hobby is managing his sisters schedule.
 * Favorite food: Fried bananas.
 * Least favorite food: None since he doesn't leave any meal in front of his sister.
 * Cause of stress: Being unable to be with his sister.