Soak perilla leaves in vinegar water for 5 minutes and rinse under running water.

Boil 1.5 cups water, 1 cup soy sauce, 0.5 cup plum extract, 0.3 cup sugar, and 0.3 cup vinegar on high heat until bubbling. Let the mixture cool completely.

Cut perilla leaves in half for easier consumption and place them in a container.

Pour the cooled soy sauce mixture over the leaves, store in the refrigerator, and let it marinate for 3 days before serving.