Some notes and questions about ~ことになる

I was studying today and I ran into this grammar point. After looking it up in different sources, I wrote the following notes. Can someone help me make sure I’ve the right information? I’m including some example sentences straight from the sources I used, and wrote some of my own. Here it is:

~ことになる (辞書形 + ことになる)

Lit. It will be decided that ~, Supposed to ~

Some kind of decision or agreement, usually by either an unspecified agent or a desire to be unspecific, was made concerning a future action, and something is to happen naturally or on its own accord because of that decision.

Example sentences:

今度、大阪会社に行くことになる。/ It’s been decided that I am to go to the Osaka company.

日本では輪車は道の左側を走ることになっている。/ In Japan, cars are supposed to be driven on the left side of the street.

来年、けっこんすることになりました。/ I’m getting married next year.

My sentences:

彼がすることになったら、いったいどうして僕がしらなきゃ?/ If he’s the one supposed to do it, why do I have to?

両親は僕が入る学校を決めることになりました。/ My parents have already decided what school I’ll enter.

すみません、今日に僕の番ですことになることを忘れた。/ I’m sorry, I forgot today was supposed to be my turn.

Thanks in advance.

I cant say too much about your sentences, but did you mean for this to be しなきゃ

also with the translation you are going for, I would use は rather than に, but I may be wrong.

Its been bothering me and im like 90% sure of it so I’ll go ahead and add that I believe it should be ことになるの. Ive only ever seen ことになる nominalized using の and ことになること sounds wrong.

Another thing that ill just throw out there. Pretty sure this doesnt work either. です is a copula and I dont think you can use it here.

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Looks like you got some information from the DoJG, one important point there is that an event takes place irrespective of the speakers volition.

If that “Lit.” in your notes means literally, then the points “It will be decided that ~” and “Supposed to ~” are an error, because literally Xことになる means something like “it turned out to be X”, there is not really an explicit decision in there. Something happens to you for some reason.

I sense some problems with your sentences (no guarantees) but I cannot really say how they should be :slight_smile:

  1. 〜たら gives some condition that happens first, so it’s more like “When it turns out to be him that has to do it, why will I have to do it.” which is something different/strange. How about なら :slight_smile:

  2. You are explicitly giving the “decider” here, this sound more like the parents are now not in control, like “It turned out that my parents had a decision on my school.”

  3. 僕の番ですこと You can’t use こと to nominalizer some something that already is a noun :slight_smile: So 僕の番になる. [The です would also look fishy, should be だ.] Other than that, になる looks into the future, but everything here is already in the past … Also, 今日 also seems a bit strange?

Finally, there is also a “ことになる” in the intermediate DoJG, where it means “end up with, cause, come to mean that”.

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Well, same, but I think honestly the second sentence should just be 両親は僕が入る学校を決めた for what hes trying to say. Idk if thats right tho, and if I had to write it I would say 両親は僕が(?)どの学校に入るか決めた, but if theres one thing ive learned since I started learning japanese its that I suck at japanese.

Which leads me to my next point that it would be a good idea to ask a native. @Leebo has a girlfriend I hear (and hes kinda smaht)

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Yeah, I purposely wrote something I know very well is beyond my skill level in order to get it wrong, and learn from it. Sorry they were so weird, and thank you ver much for replying.

Don’t 〜たら and なら work pretty similarly? I understood it as the first condition being “If he has to do the work”, etc etc. I need to read up more on those.

Oh, I see, it makes a lot of sense when you point it out that way.

My teacher told me that you can be specific about times with , for example 金曜日… “Fridays, …” 金曜日に… “That friday…” Although now that I think about it, there can’t be a more today-sy today, right? haha

I got most of my information from the basic one. Perhaps that’s where the gap lies.

At any rate, thank you very much for your reply! It was very helpful!

Yeah, now that I’m reading my mess after going to sleep I can tell I’ve made many mistakes. I purposefully went ham with my sentences to get stuff wrong. Thank you very much for the pointers!

not sure if it helps you, but I recently studied this grammar point using Tobira.
Tobira gives two seperate explanations:

  • "Verb-non-past"ことになっている means that something has been decided and the result of that decision is still in effect. Is is often used to introduce rules and customs, as well as one’s schedule.

  • "Verb-non-past"ことになった means that a situation has changed due to some external force (e.g. a decision made by someone other than the speaker). It indicates either that the speaker (or the subject of the sentence) did not actively make the decision or that he/she is viewing the decision from the standpoint of an outsider.

Basically, I can’t really help you and tell you if the sentences are correct, but from my gut feeling I would say that


The “決める” is doubled, because the sentence structure indicates that the decision was made.

Hope someone who knows some more Japanese can help, I am really interested in this.

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I was reading about the finer points, basically the た in 〜たら is the past helper verb, it is a “perfective” clause. So the first part of the sentence must be completed before the second one can happen afterwards. It also means something different when used for past events because of that.

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I did some extra research and found this really interesting article:

Aparently, ~ことになる is intransitive, and in contrast, ~ことにする is transitive as you’re deciding on something.

It’s quite informative I think.

All right. I think I’ve got it down this time.

It states that something that has been decided outside the volition of the speaker. That decision usually concerns the future or something that happened on its own accord. なる is often used in the past version, to express that something has already been decided: ことになった/ことになりました.

彼女は僕と別れることになった。/ My girlfriend has broken up with me.


I feel like most of the example sentences using ことになる don’t state the person who decided, they seem to work more like “it has been decided”.

Did you make up the last example sentence yourself?

Yeah, I did make the sentence. I was going to argue that sometimes who made the decision actually appears in the sentence, but as I looked through sentences it seems to gravitate more towards what you’ve said. Here are said sentences, straight from my books:

As the late Yamada-san was a person who disliked ceremony, it looks like there won’t be a funeral or anything.

Mr. Smith is supposed to teach English in Japan.

So, as for my sentence, I think it’s correct in terms of grammar, but incorrect in terms of translation. Looking at this new information, the translation would be something more like “It’s been decided that I’m to break up with my girlfriend”, like a failed arranged marriage or something, lmao.

Thank you for your reply!

I often think about ことにする vs ことになる as a pair of sentences. I decided to _____. But, I ended up _____.

For example:
I decided to go to Tokyo.

But, ended up going to Kyoto.

Keeps it simple, which considering the rather minuscule brain I possess, is a rather good thing. Essentially, I use ことになる to express stuff where I wasn’t the decision maker … it was someone or something else that forced the decision on me.


That contrast really helps. I also like to think that ことにする is “transitive” since you’re making the decision, and ことになる “intransitive”, as the decision is being made.

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Yep, exactly … although, for me, the linguistic terminology of “transitive” and “intransitive” always used to add a certain amount of cognitive delay when I want to utter some Japanese … these days, I just think “is someone doing … or is it changing state” … that lessens the amount of milliseconds I need to know when to use を or が :slight_smile:

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