Decisions & Happenings
Learn how to express personal decisions and external outcomes in Japanese using ことにする and ことになる.
Decisions & Happenings
Japanese draws a clear line between things you decide and things that are decided for you — or that simply happen.
ことにする expresses a personal, deliberate decision: 'I decided to do X.' The subject is the one making the choice. ことになる expresses an outcome or decision that came about externally — through circumstances, group consensus, or institutional rules: 'It has been decided that X' or 'It turns out that X.'
This する vs なる contrast mirrors the broader Japanese pattern seen in becoming (にする vs になる): する implies agency, なる implies a result that emerged on its own.
Attach ことにする to the dictionary form (or ない form) of a verb to express a personal decision.
[dictionary form] + ことにする[ない form] + ことにする
- 行くことにする (I'll decide to go)
- 食べないことにする (I'll decide not to eat)
The past form ことにした is the most common — reporting a decision you've already made. The non-past ことにする sounds like you're deciding right now.
Examples
- I decided to study abroad in Japan next year.
来年、日本に留学することにしました。
- I decided to jog every morning.
毎朝ジョギングすることにした。
- I'll go to bed early tonight. (deciding now)
今日は早く寝ることにします。
- I decided never to go to that shop again.
あの店には二度と行かないことにした。
Attach ことになる to the dictionary form (or ない form) of a verb to express an outcome that was decided externally or came about through circumstances.
[dictionary form] + ことになる[ない form] + ことになる
- 転勤することになった (it was decided that I'd transfer)
- 参加しないことになった (it was decided that I won't participate)
The past form ことになった is very common — announcing a result or decision made by others (a company, school, group). Even when you were involved in the decision, ことになった frames it as a group outcome rather than a personal choice, which is a common Japanese strategy for softening announcements.
Examples
- It's been decided that I'll transfer to Osaka starting next month.
来月から大阪に転勤することになりました。
- Under the new rules, smoking is not allowed here.
新しいルールで、ここでは喫煙できないことになっている。
- In the end, the meeting was called off.
結局、会議は中止することになった。
- It's been decided that I'll give the presentation.
私が発表することになりました。
The core difference is who decides:
- ことにする: I decided (personal agency).
- ことになる: It was decided / it turned out (external outcome).
Compare the first two examples: both result in going to Japan, but ことにした says 'I made that choice,' while ことになった says 'that's how things turned out' (perhaps the company sent you, or circumstances led to it).
- ことにしている = a personal rule or habit I maintain by choice.
- ことになっている = an established rule, custom, or arrangement set by others.
In practice, Japanese speakers often use ことになる even for their own decisions to sound humble or avoid seeming forceful — framing a personal choice as something that naturally came about.
Examples
- I decided to go to Japan. (my choice)
日本に行くことにした。
- It's been decided that I'll go to Japan. (external decision)
日本に行くことになった。
- I make it a rule to exercise every day. (personal habit)
毎日運動することにしている。
- The rule is to wake up at six every day. (established arrangement)
毎日六時に起きることになっている。