When I made natto with canned mackerel in miso sauce, the recipe suggested that this dish would be good as a drinking snack or on rice. So, I used the leftovers to make this donburi for lunch. I used frozen cooked rice which we always have in our freezer. (When we cook rice, we usually have leftovers so we freeze individual sized portions in small Ziploc bags with the date written on the outside. Then when we need rice we thaw it for 30 seconds in the microwave which makes rice to be separated but still semi-frozen. At this point, I put the rice in the bowl).
I also added precooked green beans (I usually boil a package of green beans and keep it in the refrigerator). I microwaved it with a lid on (this donbri bowl has a lid) until the rice was warm (it comes out with a consistency and taste close to freshly made).
I also added a sunny -side-up fried egg (the egg yolk still runny).
This was quite good. I should have made more sauce. I am sure freshly cooked rice would have been better but even with frozen rice, this was quite enjoyable.