矢先やさき
yasakini

Adverb

1. just when (one is about to ...); just as; the very moment when; on the point of

わたくし返事へんじをしようとした矢先やさき、彼かれくちしてきた。
watashiga henjio shiyōto shita yasakinika rega kuchio dashite kita
I was about to reply, when he boldly cut in.