This term was first used by Masahiro Yamada of Tokyo Gakugei University in his book The Age of Parasite Singles. A parasite is basically an organism that feeds off another organism but contributes nothing to the host. In Yamada’s book, he talks about how modern Japanese parents are the host, and their offspring are the parasites.
Since the 1970s this phenomenon has being steadily increasing. It is now said that in Japan, approximately 60% of men and 80% of women between 20-34 live with their parents. 85% do not help with the living expenses and 50% receive additional financial aid from their parents. Source
I’ve noticed a lot of Japanese people stay with their parents until they marry. Some say they stay with their parents because it’s too expensive to live independently. However, I think young professionals could live on their own if they adjusted some of their lifestyle choices. No more 200,000 yen bags for someone earning an average salary. No more going to fancy restaurants for dinner every night, either.
I think living on your own or at least having sharemates should be encouraged. You develop new life skills and learn to adapt to new situations. You learn to co-exist with people. This experience is like a rite of passage into adulthood.
I think living with your parents is not the problem. The problem is being parasitic. If you’re living with your parents, you should contribute money, labor, or something that benefits the family. As an adult, just your presence is no longer enough.