Always cool to see what homebrewers around the world are doing!
I brewed a sake a few years ago, sounds like a somewhat similar process (no leaves in mine though). Didn’t try to add fruit either.
If you want the sweetness of the fruit to remain you’ll need to kill the yeast (pasteurize) the rice beer before adding it. If you want the sugars of the fruit to ferment, you can add it (whole, juice, puree, dried etc.) after the initial fermentation is mostly complete.