Mix the natto with the rice and mix together while gently smashing the beans. Add sugar and continue mixing (see photo).

Add the milk and continue mixing. Cover with plastic wrap and microwave until it comes to a boil. Be careful that it doesn't boil over. Once it has cooled, warm it again in the microwave. Adding salt will bring out the flavor of the natto even more.

Chill in the freezer (mix it two times during the freezing process, as if kneading. You can add in some extra dry natto during mixing.) It will become sticky and stringy as you eat it and it starts to melt. It's so good.