杞憂 きゆう
kiyū

Noun

1. needless fear; groundless apprehension; unfounded worry

元気 げんき こえがそのまま かえってくる。杞憂 きゆうだったかな・・・。
genkina koega sono mama kaette kuru. kiyūdattakana....
Her cheerful voice responded just like that. Guess I was worrying over nothing...