Beat eggs well in a bowl. Add mirin, soy sauce and salt to the dashi, mix well then blend into beaten eggs. Coat a square omelette pan with oil and heat until a drop of egg mixture sizzles.
Pour a small portion of egg mixture and spread evenly. When the mixture is half done, roll toward front of pan and grease empty space in the pan. Slide roll to the other end, grease empty space again and add more of the egg mixture. Repeat this, making the roll bigger.
When egg roll is done, shape evenly by using a bamboo rolling mat and cut into pieces.
Serve omelette pieces with grated daikon and add a dash of soy sauce.