In a mixing bowl, combine mochi flour and sugar, then gradually stir in water until the mixture is smooth and free of lumps. Stir for 2-3 minutes until well blended.

Transfer the mochi mixture into a lightly greased steaming dish and cover it. Place the dish in a steamer over boiling water and steam for approximately 20 minutes.

Once steamed, allow the mochi to cool for about 10 minutes. Dust hands and a clean surface with cornstarch. Portion the dough into equal-sized pieces and flatten into circles about 3 inches in diameter.

Place a peeled and pitted peach half in the center of each mochi circle, fold the edges over the peach, sealing it completely.

Place the wrapped mochi on a plate dusted with cornstarch and refrigerate for at least 1 hour before serving.