Slice the green onion diagonally into 1cm pieces.

Crack the eggs into a bowl and beat them lightly.

In a small pot, combine the seasoning ingredients (sake, mirin, sugar, soy sauce, water) and bring to a boil. Add the green onion and simmer on low heat until softened.

Spread the beef slices into the pot and cook over medium heat, flipping occasionally until the color changes.

Pour the beaten eggs evenly into the pot. Once it starts to boil, cover with a lid and cook for about 1 minute. Turn off the heat and let it sit to finish cooking with residual heat.