たらOnce/when, after completion
たら can mark a completed first event as the point after which a second event occurs. It is used both for planned sequences and for reporting something discovered after the first event.
Completion comes first
The first event must be complete before the second begins. Although the first verb looks past, the whole sentence may describe the future: the past-looking form shows completion relative to the next event, not necessarily past calendar time.
A planned sequence
仕事が終わったら、駅で会いましょう。
Once work is over, let's meet at the station.
AnalyzeThe meeting is planned for the time after the work has finished.
Discovering something afterward
In a past narrative, the first action can lead to an unplanned discovery. The second clause usually describes what the speaker found, noticed, or what happened, rather than another action the speaker had deliberately planned.
カフェに入ったら、窓際に昔の友達が座っていた。
When I entered the café, I saw an old friend sitting by the window.
AnalyzeEntering the café led to an unexpected discovery; sitting by the window was not the speaker's planned next action.
Time sequence or uncertain condition?
The form たら also expresses an uncertain “if” condition. Use the temporal interpretation when completion and event order are central: first A finishes, then B occurs. If the main question is whether A will happen at all, the hypothetical use is the better analysis.
Compared with a direct before-after sequence
てから directly states that B happens after A. Temporal たら more readily presents the completion of A as the occasion or trigger for B. They can be close in some planned sequences, but they are not always interchangeable, especially in an unexpected discovery.
宿題を終えてから、ゲームをしました。
I played a game after finishing my homework.
AnalyzeThis neighboring form simply presents the two actions in before-after order.
More examples
書類を確認したら、受付に出してください。
Once you have checked the documents, please submit them at reception.
Analyze料理ができたら、みんなを呼びます。
Once the food is ready, I'll call everyone.
Analyze雨がやんだら、出発しましょう。
Let's leave once the rain stops.
Analyze部屋に戻ったら、机の上に小さな箱が置いてあった。
When I returned to the room, I found a small box on the desk.
Analyze映画が終わったら、近くで夕食を食べよう。
Once the movie is over, let's have dinner nearby.
Analyze朝起きたら、外が真っ白だった。
When I woke up in the morning, everything outside was white.
Analyze