Yunseo was born in Seoul, South Korea to a young, single mother and an unknown father. Growing up, his mother wasn’t always around, often leaving the young Yun in the care of his grandparents. He was raised knowing their actual status within his life and who his aunt was too, who was only a couple of years older than him and who he thought of as an older sister. His grandparents always tried to keep the lines of communication open between Yunseo and his mother, but she always disappointed, especially when she started putting more into her relationship with her new boyfriend who disliked Yun with a passion. So it wasn’t all that surprising when she did the exact same thing to her second son, Jiwon.
Eventually, after a long and emotional, legal battle, Yunseo and Jiwon were placed into the full custody of their grandparents, since it was obvious that things weren’t going to change otherwise. But they didn’t know what they were getting themselves into because Yunseo’s mother had gotten herself into a bad crowd and was willing to do anything to get her children back. So they fled to a place that no one would expect, Australia, where they found some protection with the Victorian Ministry of Magic because of the old connections that the family had and because of Yunseo’s grandfather’s job within the Korean Ministry of Magic.
It was a hard adjustment for Yunseo because he was leaving his friends and everyone he knew back in South Korea, and he was in a strange place where he wasn’t used to the culture or the language. There was also the fact that he was trying to hide the fact that he was a metamorphmagus and wasn't fully in control of his powers because of how stressed out he was by the whole thing. They considered him a late bloomer at age ten, especially when it was compared to his mother who had shown it during her early childhood. His grandparents had to teach him how to control it.
Yunseo was sent to Tallygarunga once the time came for him to start school. He was told to keep a low profile and not to talk about what had brought him to Australia. Yun was sorted into Sturt house and somehow managed to keep up with his side of the bargain, though there were times when a good memory charm was needed. Once he finished school he went onto VMU, where he studied Magical Education.
The year before Yunseo graduated from University he received a letter from a close relation who knew where they were telling him that his mother had died. This has still yet to sink in for him and he seems a little emotionless when talking about it.