序(つい)でにwhile (one is at it), when, on the occasion of, at the same time (as), on one's way (to), by the way, incidentally, in passing

Common

1. Adverb

   1. 1.

      while (one is at it), when, on the occasion of, at the same time (as), on one's way (to), by the way, incidentally, in passing

      Usually written using kana alone