Some might say Kohl can be a bit of an ass, and he most certainly can be if pissed off, but a lot of the time him being an ass is just his sarcastic nature which few people seem to pick up on. Most of the time Kohl will make fun of whoever and whenever he feels like it, normally making fun of his friends though as those close to him would know he's just joking. There would never be any malice intended unless of course he got pissed off, as stated above. He is often times known for having a short temper and a bit of a potty mouth, and there isn't really any reasoning behind it.
A lot of the time Kohl will get frustrated with himself, he'll get flustered when he talks and he'll end up messing up. He's his own worst enemy when it comes to these things. He also finds it hard to make friends sometimes because he's scared to put himself out there due to people not liking his sense of humour as well as the language barrier he still hasn't been able to 100% get over. Plus switching schools with only a couple weeks into his first year probably didn't help him any when it came to making friends. All this negative stuff aside, Kohl is a good kid, it just takes awhile for him to show that he can actually be a lot of fun.
Erik and Abigail Dae came from two long lines of pure-blood Korean wizards who lived in Germany. Erik's family hailed from Luxembourg, while Abigail's hailed from Heidelberg. The pair of pure-blood wizards had originally met during a triwizard cup -- as Erik attended Durmstrang and Abigail attended Beauxbatons -- and some could say it was love at first sight. They were smitten with one another almost instantly. Growing close over the time of the triwizard cup, only to be separated once it ended. Luckily for the two of them however they were both in the last years of wizarding school and after graduation they would once again be reunited after keeping in touch throughout their final year.
Within two years, they were married and expecting. After getting married the couple had moved to Erik's hometown of Luxembourg, while frequently visiting Abigail's family back in Heidelberg. Not long after moving into their home in Luxembourg, Abigail and Erik welcome little baby Kohl into the world. From the get go he was a very troublesome child, always getting into some sort of mischief. He tended to fancy colouring on the walls with blue Sharpie markers which obviously led to a repainting of the walls.
Growing up was a bit difficult for Kohl to say the least. He had a great family life, parents that cared for him deeply and what not. But it was when he made the choice to attend muggle school despite knowing of his magical abilities. Fitting in proved to be difficult for him, despite being born in Germany and German being his native language, kids his age still made fun of him for being the only Asian in the school. Needless to say muggle school didn't last long for Kohl -- and his rather cold and snappy personality to new people can be directly linked to his experience.
Safe to say it was almost inevitable that Kohl would have a magical encounter at some point. His took place when he was eight years old and he was helping his mom put candle's on his dad's birthday cake. Before Abigail had a chance to even put the lighter to the wick, Kohl had unintentionally lit the candles using magic. At this time was when Abigail and Erik began to teach Kohl more in depth about magic.
A little after his first magical encounter, the family had moved from Luxembourg, Germany to Essex, England. The move was hard for Kohl, unlike his parents he had no clue how to speak English. So by the time Kohl was meant to start attending wizarding school he attended Durmstrang instead of Hogwarts, his parents saying he could switch by the time he had a better grasp on the English language. Kohl wasn't a big fan of Durmstrang, which only motivated him to learn English quicker.
By the sixth week of school, Kohl had improved greatly in English compared to when he left England. He got stuck a little bit like any foreigner would, but he was now fluent enough to the point where Erik and Abigail felt comfortable with him attending Hogwarts. He had been fully transferred to Hogwarts the following week.