Slice the green onion into thin strips, julienne the cucumber, and thinly slice the myoga.

Mix the concentrated soy sauce base and soy milk in a bowl and chill in the refrigerator.

Boil water in a pot, cook the udon noodles according to package instructions, then rinse with cold water and drain.

Place the noodles in a serving bowl, top with shiso leaves, canned saba, green onion, cucumber, and myoga, then pour the chilled soy milk mixture over.