Put the daikon radish into cold water and bring to a boil until tender (about for 15-20 mins). Wash it with water.
Put daikon radish, squid, bonito flakes, sake, sugar in the pot and pour in enough water to cover. Simmer over low heat for 5 mins.
Add soy sauce, mirin and keep simmering for about 20 mins. Place a small lid directly on the food when simmered. Let them cool.