Trim the roots of kaiware sprouts and cut them in half.

Place the frozen udon noodles in a microwave-safe container, cover loosely with plastic wrap, and heat according to package instructions (600W).

In a pot, combine the seasoning ingredients (☆) and tuna, then heat over medium heat until boiling. Add the potato starch slurry and stir until thickened. Pour in the beaten eggs and cook until set.