small mercy in misfortune; silver lining; blessing in disguise
Used when something good or fortunate occurs within an otherwise unfortunate situation. Often said to find a positive aspect in a bad event.
I had an accident, but it was a small mercy that my injuries were minor.
財布を落としたが、中にあまりお金が入っていなかったのが不幸中の幸いだ。
I lost my wallet, but it was a blessing in disguise that there wasn't much money in it.