Hikikomori is a form of pathological social withdrawal or social isolation whose essential feature is physical isolation in one’s home. The 2010 Japanese guidelines define that a person must meet the following criteria to be diagnosed with hikiikomori: a) marked social isolation in one’s home; b) duration of continuous social isolation of at least 6 months; c) significant functional impairment or distress associated with the social isolation. Advances in the conceptualization and treatment plan are discussed.