Hikikomori

Hikikomori is a Japanese word that describes people who withdraw from society and spend extreme amounts of time on their own. The withdrawal usually happens slowly. Tamaki Saitō was the first person to use the word. In 1998 his book "Shakaiteki hikikomori--Owaranai Shishunki" was published. An English translation by Jeffrey Angles, "Hikikomori: Adolescence without End", was published in 2013. The Japanese Ministry of Health, Labour and Welfare defines hikikomori as people who refuse to leave their house for over six months. In 2010 there were 700,000 hikikomori. The average hikikomori was 31 years old. Tamaki Saitō thinks that there may be over 1 million hikikomori (1% of the Japanese population).
People who withdrew from society during school refusal is often referred to as "futōkō" (不登校).
English words with similar meanings include recluse and agoraphobic.