In a medium mixing bowl, combine the sweet rice flour, water, and sugar. Stir until the mixture is completely smooth, ensuring there are no lumps. The dough should be thick yet pourable. Cover with plastic wrap and let it sit for about 10 minutes.

Transfer the prepared dough to a heatproof dish or a steaming basket lined with parchment. Steam for approximately 20 minutes, stirring halfway through. The mochi is done when it turns translucent and slightly bouncy to the touch. Let it cool slightly.

On a clean, cornstarch-dusted surface, turn out the cooled mochi dough. Scoop out a portion and flatten it into a disc about 3–4 inches wide, ensuring the edges are thicker.

Place a ripe peach in the center of each mochi disc. Fold the edges of the dough over the peach, pinching and sealing it carefully to create a smooth ball shape.

Refrigerate the wrapped mochi for at least 30 minutes to firm up.