I created an unofficial Jujutsu Kaisen character. His name is Gunnar Skarsgaard, and he attends Kyoto Metropolitan Curse College (Kyoto Jujutsu High) as a second-year. The son of Yuki Tsukumo and Drage Skarsgaard, he's his parents' son through and through, having inherited a seemingly endless wellspring of cursed energy, and with it immense potential. He's a prodigy, and he's been through grueling training since he could walk. 
For some basic details:
The only special-grade sorcerer at Kyoto Jujutsu High. Todo is Grade 1, Noritoshi Kamo Semi-Grade 1, and Mai Zenin Grade 3. 
Height: 6'3 (191cm). He is tallest in Kyoto High after Todo (6'10, 210cm).
Weight: 210lbs (95kg)
Gunnar is a tall young man with pale skin and a burly build from a lifetime of training. His eyes are hooded, with grey irises. He is primarily of Northern European heritage, with a Nordic father and 1/4th Japanese mother. His dirty blond hair flows to his shoulders, and he is considered the most handsome boy in Jujutsu High, with attractive and mature facial features that make him appear older than he is. His Jujutsu High uniform typically consists of a traditional black Gakuran, slacks, and minimalist sneakers. In combat, he dons joggers and a muscle tee. In casual settings, a polo shirt, slacks, and loafers.
More backstory: Gunnar was born with the ability to see curses, and he began using basic cursed energy at the age of three. However, his unusual strength proved a danger to his peers, and one day he unintentionally injured many of his preschool classmates. For this reason, his parents pulled him from school. Rather than receive a home education, he pushed his parents toward a very unconventional path. He chose to live in the wilderness, honing his physical might as well as his survival skills. By age 7, he felt it got boring, however. Gunnar had already become a bit of a daredevil, so he chose to travel the world in search of legitimate challenges. He quickly found work as a nomadic mercenary, battling curses and even "troublesome" people, such as warlords, terrorists, and gangs. He did, not, however, neglect his cursed energy training. When he finally enrolled in Jujutsu High, he was stronger than most of his peers, save for the second-year (now third-year) Aoi Todo. Gunnar, however, has worked tirelessly and he's considered the second-strongest sorcerer after Satoru Gojo. He  He's good friends with Kasumi Miwa, whom he met in his first year at Kyoto High.
Personality, relationships: what you might expect of someone who grew up a mercenary. Stoic, calm, logical, but not without flaws. While he didn't spend much time in classrooms, he learned a lot from books sent by his parents as well as life experience. As he was always a precocious child with more of an independent upbringing, he can be prone to stubbornness should he disagree with others, but he respects basic decorum.  Gunnar is a very hard worker, and he likes to stick to his schedule. Five days a week, he either trains or takes on missions as much as he can, with one of these training days set aside for meditation to focus and refine his cursed energy control. The remaining two are leisure days. On leisure days, he either hangs out with friends, or women but always takes time to visit his parents and younger sister Pia. On first glance he comes off as stoic and mature, and this along with his apperance make him quite popular with them. However, his upbringing makes it difficult for him to truly commit to others, even those he has feelings for. He receives lots of attention, and he's easily tempted by women that sing his praises. In his words, friendships are easy, but romance is very difficult to navigate.
Abilities: Strong enough to lift a train car. Fast as a jet plane.