Explanation
Expresses that once a certain action happens, the situation changes irreversibly—usually in a negative way.
Formation
Verb-た form + ら最後
Detailed explanation
The たら最後 grammar point indicates that once an action (in た-form) occurs, there is no going back and an unpleasant or unavoidable state follows. Often translated as 'once...then it's all over' or 'the moment...there’s no turning back.'
Examples
Kono gēmu o hajimetara saigo, jikan no tatsu no o wasurete shimaimasu.
Once you start this game, you completely lose track of time.
Kare wa bīru o ippai nomihajimetara saigo, tomaranaku narimasu.
Once he starts drinking a beer, he can't stop.
Kono hon o yomihajimetara saigo, ikki ni dokuha shite shimaimashita.
Once I started reading this book, I ended up finishing it in one go.
Kare o okorasetara saigo, nakanaka yurushite moraenai yo.
Once you make him angry, he won't forgive you so easily.
Practice
Grammar content sourced from hanabira.org.