ずにはおかない / ないではおかない

The grammar structures ずにはおかない and ないではおかない express that something will inevitably happen or that a feeling or action cannot be suppressed. It conveys the sense that circumstances or emotions make a certain outcome unavoidable – "it will definitely…" or "it can't help but…".

Formation

• ずにはおかない: Attach to the ない-stem (未然形) of the verb + ずにはおかない

  • たべる食べる → 食べずにはおかない
  • わらう笑う → 笑わずにはおかない
  • Exception:する → せずにはおかない

• ないではおかない: Attach to the ない-form of the verb, replacing ない

  • たべる食べる → 食べないではおかない
  • わらう笑う → 笑わないではおかない

Both forms are interchangeable in meaning, though ずにはおかない is slightly more literary and formal, while ないではおかない is somewhat more colloquial.

Usage 1: Emotions or reactions that cannot be suppressed

When used with emotion or reaction verbs, this pattern describes feelings that arise naturally and cannot be held back.

This usage often appears with verbs like かんどう感動する, おこる怒る, なく泣く, わらう笑う, etc.

Usage 2: Something that will inevitably be carried out

When used with action verbs, it expresses a strong determination or the inevitability that something will certainly be done – often implying an external force, natural consequence, or unstoppable will.

Nuance

This is a written/formal expression commonly found in essays, novels, news commentary, and speeches. It emphasizes that the outcome is beyond anyone's control – whether driven by emotion, circumstance, or sheer determination. It is stronger than simply saying 〜～てしまう or 〜～ないわけにはいかない.