He spends a lot of time in front of his computer, and has a hobby of ordering things from the Internet — mostly fake magical or occultic implements— and then returning them before he has to pay, for the thrill of receiving something ridiculously stupid. He is also interested in cars and collects miniature versions of them. When he comes into possession of Shinku and winds her up, he is unwittingly and unwillingly caught in the crossfire of the Alice Game — Shinku declares him to be her "servant" and demands that he obey her at all times. Jun is extremely skilled at crafts and at sewing. Although he is arrogant, and occasionally cold and rude, he cares for others but typically refuses to let his feelings show. He is especially friendly with Hinaichigo, and at times, blushes around Shinku, which betrays that he cares deeply for her.
Initially he was a 'hikikomori', a Japanese term for people who choose to withdraw from the society due to some embarrassment that had traumatized them. In Jun's case, this was never clearly stated.. or I just wasn't paying that much attention to the humans in this anime.. hahaha..! So, anyways.. However, as time passes and he spends a lot of it with the dolls, Jun finally succeeds in pulling out of his own safe world and continue going to school. (oh, yeah. He didn't go to school after whatever it was that happened)
Jun is Shinku's medium, and later in the story he also sworn allegiance to Suiseiseki, given the circumstances, shit they were in at that time. Four of the six dolls (Suiseiseki, Souseiseki, Shinku and Hinaichigo) takes residence in his house.