This is my husband's recipe. He said this is very delicious (and I saw it was true while watching him eat), but unfortunately, I don't like egg and natto so I will have to take a photo of my own version next time-- which means I need to prepare my recipe an hour before I get hungry next time just so I can have a food pictorial.
But while waiting for my version, I suggest you give this a try!
**Natto・納豆・なっとう is a Japanese food which means fermented soybeans. It can be bought in packs of three and each pack has an accompanying sachet of sauce, usually with dashi or soup stock made from fish and other things. So if you're a vegetarian, you'll have to use soy sauce instead of that sauce pack.
**Udon・うどん is thick Japanese wheat noodles usually used in soups, and dry and fried noodle dishes.
Tips and tricks
The frozen udon I used is ready after one minute of boiling. You may use other kinds of udon but my husband's favorite kind of udon is the frozen type, and it lasts in the freezer for long so we can just pull it out anytime and quickly cook udon whenever we want.
A vegetarian for 12 years and a kitchen warrior since I moved in to Japan, my favorite battle has been winning over my husband's interestingly complicated taste buds.