I'd highly recommend the book "Hikikomori: Adolescence Without End" by Saito Tamaki, translated by Jeffrey Angles. First published in 1998 it describes the "hikikomori" social/psychological phenomenon, and ways treatment has been approached. Ultimately, Saito observes that nobody can "fix" the individual hikikomori directly— therapy must be multi-faceted, continuous, and ongoing, focused on reducing stigma and shame. And for all that, may ultimately not be effective.
> Although some studies suggest that hikikomori commit acts of domestic violence at higher rates than the general population, experts say the most pressing problem is that those with the condition, like others in Japan, rarely seek help for their mental health problems. Hikikomori may be affected by schizophrenia, depression or anxiety, or they may be on the autism spectrum.
This seems like a mental illness problem, of which "hikikomori" is one side effect. It may likely be exacerbated by a stronger need to conform to culture and/or societal expectations.