後の祭り

expressionあとのまつり · atonomatsuri

1. Englisha day after the fair; (at a) stage when it's too late

   • いまさら嘆いても、それこそ、後の祭だよ。You can regret it all you want, but it won't do you any good now.

Source: JMdict (EDRDG) · CC BY-SA 4.0 (EDRDG)