expression, adverb
without either person initiating; both doing something at the same time without a clear instigator
Used when two people perform an action together, but it is unclear who started it; often implies a natural, spontaneous mutual action.
二人はどちらからともなく手を繋いだ。
The two of them held hands without either one initiating it.
どちらからともなく笑い出した。
They both started laughing at the same time, without anyone starting it.