grammar → 一…就…
TSUMUGU · TBCL 3 (est.) · 語法
一…就… grammar point · tier 2 · 一…就… as soon as
Immediacy: the instant the first happens, the second follows.

字源 FORM what the parts do

一 marks the trigger; 就 fires the result the instant it lands.

故事 STORY a scene to remember it by

A light switch; 一 is the flick, 就 is the room already lit.
自撰記憶法
框 · Frame
一 [trigger] 就 [result]
例 · Examples
1燈一開就亮。
The instant the lamp is switched on, it's bright.