～たとたん(に) — The Very Instant
Expresses that the moment one action was completed, a second (usually unexpected or spontaneous) event happened right away. It stresses surprise and immediacy — 'the very instant that...' The second clause is typically something the speaker did not control or foresee, and is stated in the past tense.
Structure
[Verb た-form] + とたん(に)
Examples
家を出たとたんに、雨が降り出した。
Ie o deta totan ni, ame ga furidashita.
The instant I left the house, it started to rain.
出た (past of 出る) + とたんに links to an unexpected immediate event
彼は私の顔を見たとたん、泣き出した。
Kare wa watashi no kao o mita totan, nakidashita.
The moment he saw my face, he burst into tears.
見た + とたん shows a spontaneous reaction right after seeing
立ち上がったとたんに、めまいがした。
Tachiagatta totan ni, memai ga shita.
The instant I stood up, I felt dizzy.
立ち上がった + とたんに connects standing to a sudden, uncontrolled sensation
• Must use the past た-form before とたん. • The second clause describes something sudden/unexpected and is normally past tense; avoid commands or intentions. • Register: neutral; very common in narration.
Commonly confused with
The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones ～たとたん(に) is tested against.
vs たら
たとたん stresses surprising simultaneity of a single completed moment; たら is a broader conditional 'when/if' without the shock of immediacy.
vs とすぐに
とすぐに means 'soon after' and can include planned actions; とたんに demands an instantaneous, often unintended reaction.
More time expressions
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