Well, according to the software developer,
there are pieces in between .Mac and Yojimbo that change on installation that cannot be undone. You might look in the .Mac preferences to see if there's anything you can do, assuming you have .Mac (I can't see the prefs as I don't have .Mac).
But it seems to me, hmmm, there are a couple of other options to look at...
(2) Find Contextual Menu Items in the /Library folder and see if there's a plugin it left in there; if there is, trash it.
(3) Try AppZapper to further uninstall Yojimbo
(4) Try
rebuilding the LaunchServices database (at your own risk; see the later replies in this thread).