Japatan
Formation
- V辞書形 + ことになる
- Vない形 + ことになる
Explanation
This expresses a decision made by someone else (a company, school, other people) or by circumstances. Koto ni narimashita means 'it has been decided', and koto ni natte imasu describes a rule or fixed arrangement. Even for your own decision, koto ni narimashita sounds modest and polite, so it is common when announcing a marriage or a transfer.
Examples
来月から 大阪の 会社で 働くことに なりました。
It's been decided that I'll work at the Osaka office starting next month.
来週の 会議は オンラインで することに なりました。
Next week's meeting is going to be held online.
この 図書館では、食べ物を 食べないことに なって います。
In this library, the rule is that you don't eat food.
姉が 六月に 結婚することに なりました。
My older sister is going to get married in June.
Notes
Koto ni suru is your own decision; koto ni naru is a decision by others or by circumstances. Koto ni shite iru is your personal habit; koto ni natte iru is a rule.
Related grammar
Mini quiz
1会社の 決まりで、会議室では コーヒーを 飲まない（ ）。
Answer and explanation
Answer: 3 ことに なって います
'By company rules, you are not supposed to drink coffee in the meeting room.' A rule is expressed with koto ni natte imasu. The other choices are wrong in form or meaning.
2部長が 決めて、来月 私が アメリカへ 出張する（ ）。
Answer and explanation
Answer: 1 ことに なりました
'My manager decided that I will go on a business trip to America next month.' The manager decided, not the speaker, so koto ni narimashita is correct. Koto ni shimashita and you ni shimashita are about your own decision or effort.
3私は 来年の 春から ＿＿ ＿＿ ＿★＿ ＿＿。
Answer and explanation
Answer: 2 ことに
The order is 3-1-2-4: Watashi wa rainen no haru kara Toukyou de hataraku koto ni narimashita ('It has been decided that I will work in Tokyo from next spring'). Koto ni goes in the star position.
