ichidan verb, intransitive verb
happen to come; be there by chance
Describes being present somewhere by coincidence, often when something else occurs. Common in narrative and casual speech.
事故のとき、たまたま現場に来合わせた。
I happened to be at the scene when the accident occurred.
彼が来合わせてくれて助かった。
It was a big help that he happened to come by.