man who makes his own lunch to take to work
Colloquial term for a man, often a young office worker, who prepares his own bento instead of buying lunch or having someone make it for him. Implies a degree of domesticity and frugality.
Apparently, the number of men who make their own lunch is increasing lately.
He gets up early every morning to make his lunch; he's what you'd call a bento-making guy.
弁当 is the general term for a boxed lunch, while 弁当男子 specifically refers to a man who makes his own bento.
弁当女子 is the female counterpart, referring to a woman who makes her own bento, though the term is less common.
Compound of 弁当 (bento, boxed lunch) and 男子 (danshi, young man). A modern colloquial coinage reflecting changing gender roles and economic awareness.