Add Mochiko and water in a glass bowl and mix well. Continue adding more water if it’s too dry; about 1 Tbsp at a time.
Steam Mochiko dough (leaving dough in bowl) in a steamer for 20 minutes.
Transfer the steamed mochi into a pot and cook at medium to medium low heat with sugar (1/4 cup) until dissolved. Continue adding sugar and mix well. Ensure sugar is melted but be careful not to burn.
Transfer the hot mochi from the pot onto a sheet pan liberally dusted with potato starch or cornstarch.
Cut some mochi out and wrap the mochi around a ball of red bean paste (size of a heaping tablespoon). Pinch the end of mochi to seal. Serve with seam side down.