When I lived in Japan in the 2000's, I saw an NHK English language program on the phenomenon know as 'hikikomori', social situations where young people withdraw from society - their schools, jobs and so forth, and hide in their parent's homes. Their isolation can go on for months and even years and can have a disastrous impact on the family.
It is a cause of deep shame for Japanese families and often as not, they simply don't talk about it. The young person stays in their house or bedroom and never goes outside, so the secret can be kept, or be seen to be kept. Case in point was my next door neighbour, whose teenage daughter I never knew about - never knew existed- until one day shortly before leaving Japan, he told me about her.
On another occasion that I think I have related before, I had some dental work done in exchange for an English class. But that was actually a ruse on the part of the dentist who really wanted us to meet her son, yet another hikikomori. We did and I hope that he was the better for it. He was a personable young man.
Today I watched a CNA program on 'johatsu' - literally 'evaporated' people, those who choose to disappear completely, often with the help of professional 'movers', or even on their own using manuals such as (I kid you not) 'The Complete Manual of Disappearance'. The program was sad, especially for those left behind, who get no warning. A loved-one leaves for work or some routine activity one day and never returns.
People have lots of reasons to disappear I guess. Women in terrible domestic abuse marriages, men who feel that they are trapped in the wrong place and the wrong job, doubtless folks with debts or facing legal troubles, so many ways one might feel so desperate that they have to get out.
Just imagine someone you love walking out without warning, without a hint that anything was wrong. Imagine.