expression
once-in-a-lifetime request; extremely important plea
A dramatic, heartfelt expression used when begging for something as if one's whole life depends on it. Often used in serious or emotional appeals.
後生一生の頼みです。どうか助けてください。
This is the request of a lifetime. Please help me.
後生一生の頼みだから、この秘密は誰にも言わないでくれ。
I'm begging you as if my life depended on it—please don't tell anyone this secret.
Similar in meaning but less dramatic and more commonly used in everyday requests. 後生一生の頼み carries a heavier, more desperate tone.
A fixed expression combining 後生 (ごしょう, 'afterlife' or 'future life') and 一生 (いっしょう, 'whole life'), literally 'a request of the afterlife and this life', emphasizing the utmost importance of the plea.