LESSON NOTES · レッスンノート

N4Grammar, one piece at a time · Sep 13, 2026

てしまう and ちゃった: the grammar of "oops, I did it

〜てしまう marks an action as finished and done with — and depending on the verb, that finality either means "completely" or "oh no, I did it."

Textbooks usually give you one of those two meanings and leave the other for a later chapter. That is why learners hear べちゃった in a show, translate it as "I ate it," and miss the entire emotional point of the line. The regret is not in the words around it. The regret is in the grammar.

The basics

What does てしまう actually mean?

しまう on its own means "to put away" — to close something up, to finish with it. Attached to a te-form verb, it keeps exactly that feeling: the action is not just done, it is shut. There is no going back.

That single idea splits into two readings depending on what kind of action it is:

  • Completion — the action was carried all the way through. Nothing left.
  • Regret — the action is finished and it cannot be undone, which is bad news.

宿題しゅくだい全部ぜんぶやってしまいました。 — I finished all my homework. (completion — neutral, even a little satisfied) 財布さいふをなくしてしまいました。 — I lost my wallet. (regret — the finality is the problem)

Same grammar. Opposite mood. The verb decides.

How do you build it?

Take the te-form of the verb and attach しまう. Then conjugate しまう normally, like any う-verb.

Form Shape Example
Polite present 〜てしまいます わすれてしまいます
Polite past 〜てしまいました わすれてしまいました
Plain past 〜てしまった わすれてしまった
Contracted past 〜ちゃった わすれちゃった
Contracted (で verbs) 〜じゃった んじゃった
Negative 〜てしまわない わすれてしまわない

Because it is built on the te-form, verbs that take で instead of て give you でしまう — んでしまう, んでしまう, んでしまう. Nothing new to learn there; the te-form rules already decided it for you.

切符きっぷをなくしてしまいました。 — I lost my ticket. (polite past — the standard "I've done something bad" sentence) ケーキをべてしまいました。 — I ate the cake. (polite past — with the clear implication that I shouldn't have)

Which meaning is it — completion or regret?

Ask whether the action is the kind of thing a person would want to undo.

Verbs of achievement — わる, やる, む, く, 片付かたづける — pull toward completion. Verbs of loss, breakage, error, or forgetting — なくす, わすれる, こわす, とす, 間違まちがえる — pull toward regret. And a neutral verb like べる can go either way, decided entirely by the situation.

このほん一日いちにちんでしまいました。 — I read this whole book in one day. (completion — mildly impressed with myself) かあさんのケーキをべてしまいました。 — I ate my mother's cake. (regret — she was saving it)

This is why translation alone will not teach you this grammar point. "I ate the cake" is the same English sentence in both directions.

What is ちゃった?

It is てしまった, worn down by speech. ては → ちゃ is the same contraction you see in 〜てはいけません becoming ちゃいけない, and it works identically here.

おくれちゃった。 — I'm late. (casual — the ちゃった carries the "sorry!") 全部ぜんぶちゃった。 — I watched the whole thing. (casual — binge-watched, completion with a hint of "I couldn't stop") こわしちゃった。 — I broke it. (casual — apologetic)

ちゃった is the form you will hear most in anime, in real conversation, and from anyone who is not currently writing a report. Learn to recognize it before you learn to produce it.

Beyond the basics

Why does ちゃった sound softer than しまいました?

Both say the same thing, but the contraction makes the whole sentence smaller — and a smaller sentence sounds like a smaller problem. おくれちゃった lands like "ah, I'm late"; おくれてしまいました lands closer to "I have arrived late, and I acknowledge this." Which one you pick depends on the same polite-or-casual switch that governs everything else, but there is a second layer: the contracted form also downgrades how serious you are making the mistake sound.

That cuts both ways. If you actually broke something expensive at work, ちゃった is the wrong choice, because the grammar itself will make you sound like you don't care.

How is it different from just using the past tense?

The plain past reports. てしまう reports and editorializes.

Sentence What it says
財布さいふをなくしました I lost my wallet. (a fact)
財布さいふをなくしてしまいました I lost my wallet. (a fact, plus: this is bad, and it's final)
宿題しゅくだいをしました I did my homework. (a fact)
宿題しゅくだいをしてしまいました I got the homework done. (a fact, plus: it's fully finished, off my plate)

Learners often ask which one is "correct." Both are. Dropping てしまう is never a grammar error — it just deletes the feeling.

What about てしまおう and てしまえ?

Push しまう into the volitional and you get "let's just get this over with," which is a very natural way to talk about an unpleasant task.

いまのうちにやってしまおう。 — Let's just get it done now, while we can. (casual volitional — "while there's time") べちゃおう。 — Let's just eat it. (casual contracted volitional — the "why not" version)

The imperative てしまえ exists too, and it is aggressive: わすれてしまえ = "just forget it (and I mean it)." You will hear it in anime during a dramatic moment far more often than you will ever need to say it.

Does it work with the negative?

Two different negatives here, and learners mix them up constantly.

  • 〜てしまわない — negates しまう itself. Rare, and usually appears in warnings: わすれてしまわないように = "so that you don't end up forgetting."
  • 〜ないでしまう — not a thing. Do not build this.

If you want to say "I didn't do it," you do not need this grammar at all. しませんでした is the whole answer. てしまう is for things that did happen.

わすれてしまわないように、メモしておきます。 — I'll write it down so I don't end up forgetting. (polite — a purpose clause, very common in the workplace)

Why do sad scenes in anime always have てしまう?

Because んでしまう is not the same sentence as んだ. The grammar adds the irreversibility, and irreversibility is what makes the line hurt.

かれんでしまった。 — He died. (and there is nothing to be done about it) みんなってしまった。 — Everyone left. (and they're not coming back)

If you watch with Japanese subtitles, this is one of the easiest patterns to start noticing on purpose. The English subtitle almost never shows it, because English carries that weight with tone of voice instead of grammar. Which means the subtitle is not wrong — it just lost the part you are trying to learn.

Common mistakes

  • Using the dictionary form. べるしまった is not a sentence. It has to be the te-form: しまった. If your te-form is shaky, that is the real bottleneck, not this grammar point.
  • Forgetting that で verbs give じゃった. んでしまった contracts to じゃった, not んちゃった. The te-form already told you which one; the contraction just follows it.
  • Adding てしまう to good news. 合格ごうかくしてしまいました sounds like you are apologizing for passing the exam. For genuinely good outcomes, plain 合格ごうかくしました is correct. The exception is bragging-as-a-joke, which is exactly as risky in Japanese as it is in English.
  • Using ちゃった in a formal apology. The contraction shrinks the apology along with the sentence. In an email to a client, you want てしまいました, or something stronger.
  • Reading every てしまう as regret. んでしまった after a good book is not regret. Check the verb before you assume the mood.

Practice

Each answer is hidden — decide on your version first, then open it. Questions 4 and 5 are a pair: the only difference is the verb, and it changes the whole meaning.

1. Put わすれる into 〜てしまいました form.

Show answer

わすれてしまいましたわすれる is a る-verb, so the te-form is わすれて, then attach しまいました.

2. Contract としてしまった into casual speech.

Show answer

としちゃった — てしまった becomes ちゃった. The て disappears into the ちゃ.

3. Contract んでしまった into casual speech.

Show answer

んじゃった — this verb takes で in the te-form, so the contraction is じゃった, not ちゃった. Compare with question 2, where the te-form was て.

4. Is this completion or regret? 部屋へや片付かたづけてしまいました。

Show answer

Completion片付かたづける (to tidy up) is an achievement verb, so the finality is a good thing: the room is fully done. No regret implied.

5. Is this completion or regret? 部屋へやよごしてしまいました。

Show answer

Regretよごす (to make dirty) is a verb of damage, so the same finality becomes bad news: I made the room dirty and now it is done. Same grammar as question 4, opposite mood, decided only by the verb.

6. Something is wrong here: 切符きっぷをなくすしまいました。

Show answer

切符きっぷをなくしてしまいました — しまう attaches to the te-form, never the dictionary form. なくす → なくして → なくしてしまいました.

7. Turn 今日きょうやる into "let's just get it done today" using this grammar.

Show answer

今日きょうやってしまおう — the volitional of しまう is しまおう. Casual contracted version: 今日きょうやっちゃおう.

8. Which is more appropriate in an email to your boss: おくれちゃいました or おくれてしまいました?

Show answer

おくれてしまいました — the contraction ちゃ makes the whole sentence casual, which makes the apology sound smaller than it should. Keep the full form when the mistake matters.

9. What is the difference between 財布さいふをなくしました and 財布さいふをなくしてしまいました?

Show answer

Only the feeling — both mean "I lost my wallet." The second one adds that it is final and this is bad. Neither is more correct; dropping てしまう just removes the emotion.

10. Why does んでしまった hit harder than んだ?

Show answer

Because てしまう adds irreversibility — しまう means to close something away. It marks the death as something that cannot be undone, which is why anime uses it in the scenes that are supposed to hurt.

FAQ

Can I always replace てしまう with ちゃう? In casual speech, yes — the meaning is identical. In writing, formal speech, or a real apology, no: use the full form. And remember that で verbs take じゃう, not ちゃう.

Does てしまう always mean something bad happened? No. With verbs of achievement it simply means the action was completed all the way through, with no negative feeling at all. 全部ぜんぶんでしまった is a normal, slightly pleased thing to say.

What is the difference between てしまう and ておく? ておく means doing something in advance, for later benefit. てしまう means finishing something off, done with it. っておく = "I'll buy it ahead of time"; ってしまう = "I went and bought it (and now it's done)."

Why do I hear しまった on its own? しまった as a standalone exclamation means "damn it" / "oh no" — the same grammar, with the verb dropped entirely because the situation makes it obvious. It is the single most useful word in this article.

Is 〜てしまいました rude? Not at all — it is the standard polite form and appropriate everywhere. If anything it sounds more responsible than the plain past, because it acknowledges that what happened matters.

Vocabulary from this article

Tap the block to select all of it, then copy. In Anki: File → Import, note type Basic, separator Tab — the first column becomes the front, the second the back.

しまう	しまう — to put away, to finish with
忘れる	わすれる — to forget
なくす	なくす — to lose (something)
落とす	おとす — to drop
壊す	こわす — to break (something)
汚す	よごす — to make dirty
片付ける	かたづける — to tidy up, to clear away
間違える	まちがえる — to make a mistake
遅れる	おくれる — to be late
死ぬ	しぬ — to die
飲む	のむ — to drink
読む	よむ — to read
食べる	たべる — to eat
財布	さいふ — wallet
切符	きっぷ — ticket
宿題	しゅくだい — homework
部屋	へや — room
合格する	ごうかくする — to pass (an exam)
メモする	メモする — to jot down a note
全部	ぜんぶ — all, everything

I'm Yuuki, a Japanese teacher based in Tokyo. I've taught on italki as a Top 1% teacher and watched over 1,500 anime, and this is the grammar point where students most often understand the form perfectly and still miss the meaning — because the textbook sentence and the anime line look identical on the page.

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Sources: the author's own lessons and standard reference grammars.

More drills like the ones above, plus a timed JLPT-style mock test: Practice · N4

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