Yuga initially appears to be a vain and prideful person, thinking of himself as superior to the rest of his classmates, especially in regards to his Quirk. He exhibits extremely flamboyant mannerisms, is fond of posing, and likes to grab the attention of those around him despite frequently getting ignored by his peers. His expression rarely changes from a closed smile, even while he speaks or gets hurt, and he’s also prone to getting upset if interrupted or questioned. Yuga’s sentences often end with a star (☆) symbol, indicating a fancy tone. He also tends to play up his French heritage, occasionally implementing French words into his sentences.
However, this persona is shown to be a façade, as Yuga holds severe insecurities and guilt due to the true nature of his Quirk and upbringing. Born Quirkless, he found himself struggling with being “different” from everybody, something his parents worried about even more, not wanting him to suffer from the discrimination. This directly led to them contacting All For One, who gave him his Navel Laser Quirk, but as a result, forced their family into his debt and Yuga as an unwilling double agent, in fear of death.
Though he has a desire to have friends, Yuga rarely has the confidence to act upon it. This is initially believed to be due to his insecurities and lack of social skills; he can unintentionally come off as “creepy” to others when he genuinely means well. But this is later demonstrated to be from the guilt of having to work for the villains and betraying his classmates, thus putting them all in danger, believing himself to be unworthy of having friends, due to being a “despicable villain”. Instead, he opts to self-isolate, seen through his eating of school meals alone rather than with the members of his class and general avoidance of most social situations. Despite this, he’s been shown to be rather observant, able to pick up on Ochaco Uraraka‘s crush on Izuku Midoriya before she even realized it herself.
Yuga does possess a compassionate side and is shown to sympathize with Izuku, due to the both of them having what he perceives as highly self-harmful and uncontrollable Quirks, although the way in which he displays this sympathy initially startled Izuku, with the latter unaware the messages being also subtle cries for help. Izuku has stated that he’s never been able to read Yuga due to his unpredictable nature, although he still ended up befriending him. Though when Yuga discovers the truth about One For All and Izuku also having been Quirkless just like him, it throws him even deeper into despair, seeing just how much Izuku has fought for his beliefs and to protect others, while Yuga aids his mortal enemy.
Despite seeing himself as an irreprehensible villain, Yuga is a genuinely kindhearted person with a desire to do good. He shows this during the Provisional Hero License Exam, when he was willing to throw away his chance at a license to give Tenya Ida the chance at passing. Even during the Quirk Training Camp, despite being the one who leaked the location, he still acted to save Fumikage Tokoyami and nearly save Katsuki Bakugo when they were captured by the villains. Once All For One is arrested, Yuga lets himself slowly be more open and friendly with everyone, believing he can move on with All For One incarcerated and the lives of him and his parents no longer in danger, but after his escape from Tartarus, the fear and dread once again eats away at his own existence.
After he is exposed as the “U.A. Traitor”, he considers himself as someone who should be locked away all alone for his pathetic and heinous actions in order to pay for his crimes. However, to his disbelief, the rest of Class 1-A, as well as his teacher Shota Aizawa, recognize him as a victim of circumstance who never actually carried any villainous intentions. Instead, they want him to earn their forgiveness by helping them, a conclusion Shota helps him to reach by helping to fight back against the fear and despair that All For One planted within him. Despite his own great fear and now having an uncertain future due to his betrayal, Yuga manages to deceive All For One with the help of his friends and stands against him with Izuku, determined in bringing down the villain’s reign of terror once and for all.