Finally, after around two weeks of not tweaking #IchiBunZutsu 🙈 Just deployed to production: furigana would be shown on hover or click (works on mobile browser as well!).
I've been playing around with environment variables (+ other stuff..) with Next.js & Vercel -- and am now happy to announce that now you don't need a WaniKani account to access Ichi Bun Zutsu (ichibunzutsu.vercel.app)