Jaaki was born in Hokkaido, Japan, but was cast away by his birth parents, believed to be cursed because the red tint in his otherwise brown eyes. The only things he took away from his birth parents are his name, meaning evil, cursed, etc, and the fact that he's half-Ainu, a minority only recently given proper rights in Japan. Despite growing up either with sympathetic families or foster care, Jaaku was consistently shunned, abused, or forced to leave, until eventually, around his sixteenth birthday, he ran away and ended up in Aomori. He spent his winter break finding a job, ending up at a cafe on the first floor of an apartment building, and then went about finding the correct documentation to make him legally responsible for himself. The owner of his job was also the owner of the apartment building, and with Jaaku now using colored contacts to keep people from thinking he was some sort of demon, the older gentleman took pity on the boy, and gave him a studio apartment that was available in the building. For the first month, he could live there free, then after he would pay rent, and the deposit, from working in the cafe.

Jaaku is still pretty cold to people when he's not being paid to be nice. But he has found a niche in the host club, and is content there.

Jaaku doesn't really "hang out" with people because of his busy schedule, when he's not at school, at the host club, or at work, he's typically doing homework. He rarely even has time for sleep during the week, so he'll catch up on the weekends. He's never really tried to make friends, but he's definitely not opposed to someone being patient enough with his schedule to find time to spend with him. He's somewhat close with the other host club members, but tends to avoid the extra outings due to time constraints.

Jaaku doesn't really think highly of family. Most people he was supposed to call family cast him away or cursed at him, and it never brought about good relationships. Jaaku's family right now consists of his dog, Houki. Though he mentally uses the Kanji for "abandonment" for his dog's name, he usually will use the Kanji for "broom" when writing down the dog's name. He figured they could both have cursed names, since he found the Samoyed abandoned by his previous owner outside an old house.

He'd never admit it out loud, but the other members of the host club is also something like a family to him, as he knows even though he's not particularly close to any of them, he could still go to them if he ever had a problem.

Even though Jaaku can rub people the wrong way occasionally, he's actually rather polite, though distant, when first meeting people. It's when people try to find out more than surface facts do they come across Jaaku's true tsundere personality.

Jaaku has never really had time for a significant other. He does like to play around when he has the time though, and he's fooled around with girls, and a few guys, on slightly freer weekends. He's not opposed to a committed relationship, but doesn't really have much time for "true love" right now.