https://bugs.winehq.org/show_bug.cgi?id=54135
--- Comment #4 from Steve Metcalf metcalsr@gmail.com --- (In reply to Rafał Mużyło from comment #2)
These hovering boxes break under wine.
Elaborate how.
Though I may have a hunch why - untestable without an account on koohii.
Sorry for the late reply. Here's, some Japanese text: 「テスト」
If you copy that to your clipboard, it will appear in the search bar at the top and provide a translation below, if you hover over any Japanese text in the program the popup should appear.
You do not need any accounts to utilize this program. From my understanding, it sends your text as a series of EDICT queries.