N4 · Structured courses

Koto Ni Suru / Koto Ni Naru: Decide / It Is Decided

Learn the crucial difference: ことにする (personal decision) and ことになる (external decision/outcome). This lesson combines form, context, examples, common mistakes, and practice so you can use the pattern in real communication.

12 minNihongo Hub Editorial TeamPublished 2026-06-06Updated 2026-06-06

Learning objectives

  • Lesson goals: Learn the crucial difference: ことにする (personal decision) and ことになる (external decision/outcome).
  • Form and connection: [Verb辞书形/なi-adjective] ことにする / ことになる
  • Nuance in real use: ことにする and ことになる precisely demarcate "my will" from "the world's arrangement" — Japanese lets you clearly mark this boundary in every decision.

Form and connection

[Verb辞书形/なi-adjective] ことにする / ことになる

Core Explanation

Learn the crucial difference: ことにする (personal decision) and ことになる (external decision/outcome).

Cultural Note

ことにする and ことになる precisely demarcate "my will" from "the world's arrangement" — Japanese lets you clearly mark this boundary in every decision.

Practical examples

I've decided to go to Japan next year.
It's been decided that I'll transfer to Osaka next month.
I make it a point to jog every morning.

Common pitfalls

Build the base form before adding the pattern

Complete the required conjugation first. Do not keep polite and plain endings at the same time.

Match politeness to the situation

The examples are reliable starting points; relationships and context can still change the most natural wording.

Practice and answers

1. Write the connection formula for this lesson.
Show answer[Verb辞书形/なi-adjective] ことにする / ことになる
2. Explain the meaning of the first example.
Show answerI've decided to go to Japan next year.
3. Rewrite the final example using this lesson pattern.
Show answer毎朝まいあさジョギングをすることにしています。 ([Verb辞书形/なi-adjective] ことにする / ことになる)

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