unfortunately; regrettably; sad to say
A formal or written adverbial phrase used to introduce an unfortunate situation or outcome. Often appears at the beginning of a sentence.
Unfortunately, the plan ended in failure.
Sad to say, he died young.
Formed from the na-adjective 不幸 (unfortunate) combined with the continuative form of する (して), literally 'being unfortunate'. The phrase functions as a fixed adverbial expression.