“〜ka to omou to・ka to omottara”: No Sooner 〜 Than 〜 (a sudden, unexpected change) [JLPT N2]

Content by NTJ Kuma · Nihongo to Japan editorial team · Updated July 27, 2026

“No sooner had he come home than he went out again” — two events in quick succession, with a sense of surprise

「泣いていたかと思うと、もう笑っている」 — crying one second, and then …

「さっきまで泣いていたかと思うと、もう笑っている」 (crying until a moment ago, and then already laughing) — 「〜かと思うと／かと思ったら」 expresses “no sooner ～ than ～, just when I thought ～ then ～”: one thing has just happened, and right after comes a contrasting, unexpected change. This guide covers 「かと思うと」's use and attachment, separating it from the instantaneous 「とたん」 (N2).

Core: no sooner ～ than (right after, unexpectedly) ～

「(verb た-form／dictionary form) ＋ かと思うと／かと思ったら」 = “no sooner ～ than ～, just when I thought ～ then ～” — the first thing has just happened (or I've just thought so), and the second appears right after, unexpectedly, often forming a contrast:

• 空が暗くなったかと思うと、大粒の雨が降ってきた (no sooner had the sky darkened than big drops of rain fell).
• 泣いていたかと思ったら、もう笑っている (crying one moment, then already laughing).

Feel: “no sooner … than (suddenly) …” — the core is “right after, fast change, often with surprise or contrast” (cry↔laugh, dark↔rain). The second clause is usually an observed change beyond one's own will (like 「とたん」), so the second clause takes no will/command of one's own.

Attachment & second-clause traits

Examples in context

• 息子は帰ってきたかと思うと、すぐまた出かけた。(No sooner had my son come home than he went out again.)
• 静かになったかと思ったら、また騒ぎ出した。(No sooner had it gone quiet than the noise started again.)
• 晴れていたかと思うと、急に土砂降りになった。(It was clear one moment, then suddenly a downpour.)
• 赤ちゃんは寝たかと思ったら、すぐ泣き出す。(No sooner does the baby fall asleep than it starts crying.)
• 彼は怒っていたかと思うと、次の瞬間には笑っていた。(He was angry one moment, and the next was laughing.)

⚠️ Easy traps to avoid

① The second clause is ‘an observed unexpected change,' not one's own will/command. 「かと思うと」's second clause is usually a change the speaker observes, beyond their control (a sudden shift in others, in nature), with surprise, contrast. So it can't take the speaker's will, command, or request (×帰ったかと思うと、寝よう). For “after doing A, (I'll/please) do B,” use 「たら」 (帰ったら寝よう). かと思うと specifically depicts the observation “no sooner …, (unexpectedly) than ….”

② 「かと思うと」 carries ‘contrast, surprise,' more of a reversal than the plain 「とたん」. Both mean “no sooner … than …,” but 「とたん」 plainly stresses ‘the instant, suddenly' (開けたとたん、猫が飛び出した); 「かと思うと」 carries more of a ‘before/after contrast, reversal, changeability' (泣いていたかと思うと笑う = cry↔laugh reversal; 晴れたかと思うと雨 = clear↔rain). To stress “just like this, then suddenly the opposite (a reversal, changeability)” use かと思うと. (とたん: see 〈とたん〉.)

③ Different from 「のかと思う (mistaken assumption)」. 「〜かと思うと」 (no sooner … than …, instant change) and 「〜のかと思う」 (I thought …, a mistaken assumption) are different patterns. かと思うと = no sooner … than … (an instant contrasting change, followed by the immediate event); のかと思った = I thought … (a mistaken assumption, turned out otherwise) (もう終わったのかと思った = I thought it was over). Check whether the second part is “an immediate change (かと思うと)” or “(my) assumption/misunderstanding (のかと思った).”

🔄 Compare: かと思うと／とたん／や否や／たら

💡 Quick takeaway

「〜かと思うと／かと思ったら」 = no sooner ～ than (right after, unexpectedly) ～, its core “one thing has just happened, and right after comes a contrasting, unexpected change” (泣いていたかと思うと笑う; 晴れたかと思うと雨). Three points: ① the second clause is an observed unexpected change — it takes no own will/command (that takes たら); ② it carries ‘contrast, reversal, changeability,' more of a reversal than the plain-instant 「とたん」 (cry↔laugh, clear↔rain); ③ don't confuse it with 「のかと思った (I thought … mistakenly)」 — かと思うと is a “no sooner … than …” change, のかと思った a “I thought …” misunderstanding. To vividly depict “one second like this, the next the opposite” changeability and contrast, かと思うと is the most vivid.

❓ Common questions

Q: 「かと思うと」 and 「とたん」 both mean ‘no sooner … than …' — how do I tell them apart?

Whether there's a ‘contrast, reversal' flavor. 「〜とたん（に）」 = the instant (I finish) … (suddenly) … (plainly stressing ‘at the instant the prior action completes, the second abruptly occurs,' the point being ‘instant, sudden'): ドアを開けたとたん、猫が飛び出した (the instant I opened the door, a cat shot out — stressing the suddenness at “the moment of opening”). Its point is temporal immediacy, suddenness, not necessarily a reversal. 「〜かと思うと／かと思ったら」 = no sooner … than … (besides immediacy, stressing ‘the before/after contrast, reversal, changeability'): 泣いていたかと思うと、もう笑っている (crying one moment, then already laughing — stressing the strong “cry↔laugh” reversal); 晴れていたかと思ったら、急に雨 (clear one moment, then suddenly rain — the clear↔rain reversal). It's often for “just like this, then suddenly the opposite/different,” with a “so fast, so changeable” surprise. Test: plain “no sooner … than (suddenly) …” → とたん; “just …, then (the contrasting/opposite) …” (with reversal, changeability) → かと思うと. So to describe someone's mood swings (crying then laughing), fickle weather (clear then rain), 「かと思うと」 is most vivid; for a plain sudden event after an action, 「とたん」. (とたん: see 〈とたん〉.)

Q: Can 「かと思うと」 be followed by 「〜しよう (I'll do)」「〜してください (please do)」?

No. 「〜かと思うと／かと思ったら」's second clause must be a change the speaker ‘observes,' beyond their own will (usually others' actions, sudden natural shifts), so it can't take the speaker's will, command, request, or invitation. For example:

• ○ 弟は帰ってきたかと思うと、すぐ寝てしまった (no sooner had my brother come home than he fell asleep — observing his change)
• × 家に帰ったかと思うと、すぐ寝よう (× — 「寝よう」 is one's own will, not allowed)
• × 泣いたかと思うと、笑ってください (× — 「笑ってください」 is a command, not allowed)

If you want “after doing A, (I'll) do B／(please) do B” with your own will or a command, use 「〜たら」 (家に帰ったら、すぐ寝よう = after getting home I'll sleep right away) or 「〜てから」. 「かと思うと」 only objectively depicts the change “no sooner …, (unexpectedly) than (right after, contrastingly) …,” its subject usually third person or a natural phenomenon, the second clause a result you observe, not a command you issue. Remember: かと思うと takes ‘an observed unexpected change,' not ‘your own will/command.'

🖊️ Practice Questions (5)

Q1. 「子供は遗んでいた___、いつの間にか寝ていた。」（was playing just now, and before you knew it, fell asleep）

(A) かと思うと　(B) からには　(C) ものの　(D) わりに

Q2. 「かと思うと」の前は?

(A) Verb た-form　(B) Dictionary form　(C) ない-form　(D) て-form

Q3. 「帰ったかと思ったらすぐ出かけた」の意味は?

(A) Just came home and immediately went out again (an abrupt, unexpected change)

(B) Hasn't come home yet

(C) Has been home the whole time

(D) Doesn't plan to go out

Q4. 「かと思うと」の後件の特徴は?

(A) Unexpected, rapid change

(B) Slow, long-term change

(C) A command

(D) A pure condition

Q5. 接法が自然なのは?

(A) 晴れたかと思うと、また降ってきた。　(B) 晴れるかと思うと降った。

(C) 晴れてかと思ったら。　(D) 晴れかと思うと。

Answer Explanations

1. (A) かと思うと ── Was playing and in a blink fell asleep (unexpected change).

2. (A) Verb た-form ── た-form ＋ かと思うと.

3. (A) ── Just came home and immediately went out again.

4. (A) ── The following clause is unexpected, a rapid change.

5. (A) ── 「晴れたかと思うと」 (verb た-form) is correct.