I'm confident that either this already exists in Japanese or that apps/tools can do it.

Japanese Children learn Kanji with Furigana, so there are solutions for them.

Some examples I found:

- https://support.microsoft.com/en-us/office/use-furigana-phon...

- http://www.furiganizer.com/static/about.html

- https://www.youtube.com/watch?v=2Fmw2IrRUXo