The sauce : In a small bowl, add water, sake, mirin, soy sauce, sugar, and dashi powder.
Eggs : In a small bowl, add egg and beat it.
Onion : Slice the onion thinly.
Let's make!
In a small or medium pot, add onion, water, and the sauce you just made. Turn the heat to medium.
When the onion get's soft, turn the heat to low medium.
Add tonkatsu first then add the 2/3 beatenegg on top or around the tonkatsu. Cook until the egg is cooked, then turn the heat off. Add the rest of the beaten egg, then quickly cover with a lid and leave it for 3 minutes.
After 3 minutes, open the lid.
Let's serve!
In a deep bowl, add cooked rice first. Then add the tonkatsu on top! You can add green onion as a topping!