expression
if I don't go, who will?; what will happen to the world without me?
Archaic, grandiose expression of self-importance, used when someone declares that only they can accomplish a great task. From classical Chinese rhetoric; not used in modern conversation.
「乃公出でずんば」と彼は大げさに言い放った。
"If I don't go, who will?" he declared grandiosely.
From classical Chinese. 乃公 (lit. 'this lord') is an archaic self-reference, and 出でずんば is a classical conditional meaning 'if (I) do not go out'. The phrase is a set expression of self-importance.