This is sad. I’m not sure there is a psychological profile to identify anyone with here. When you have 120M people packed into a place the size of California, you get the most polite people on earth, as well as those who don’t fit it — like any country, some have a few screws loose. If you lose your wallet on the subway in Tokyo, there’s an excellent chance you will get it back, with all the cash and credit cards. As a stereotype, the Japanese are very self-effacing, you don’t see them showing off that much. Under this calm surface is jealousy, which I would suspect was one of the drivers here.
In Japan, the term for a young male who lives with his parents at home like this is “hikikomoro” — typically they are into anime, online gaming and other anti-social kinds of behavior and many of these individuals never leave their room. They are unemployed, don’t have friends and their parents have been known to hire “rent-a-girlfriends” to lure them out. There is definitely a cultural component to this malady and I have to admit I feel compassion for the victims and the perpetrator.
