noun, noun which may take the genitive case particle 'no'
never returning; dying
A literary expression for death, almost exclusively used in the fixed phrase 不帰の客となる (to die, to become one who never returns). Not used in everyday speech.
See also: 不帰の客となる
He passed away (lit. became a guest who never returns).
"不帰の客" is a literary euphemism for death.