昔の友達に

to an old friend

→ 昔
phrase Rare #21,083
to an old friend 昔の友達 means a friend from the past; に marks the person someone meets or contacts, or the recipient of an action.
JA: 昔の友達に手紙を書いた。
EN: I wrote a letter to an old friend.

東京駅でたまたま昔の友達に出会った。

I happened to run into an old friend at Tokyo Station.

私は道で偶然昔の友達に出会った。

I ran into an old friend by chance on the street.