Cut off the stems of the shiso leaves and slice them lengthwise in half. Remove the pits from the umeboshi and roughly mash them.

Place the sanma fillets skin-side down and pat dry with a paper towel.

Spread 1/4 of the mashed umeboshi on each fillet, place 2 shiso leaves on top, and roll them up. Secure the rolls with toothpicks. Repeat to make 4 rolls.

Heat salad oil in a frying pan over medium heat. Add the rolls and cook for 1–2 minutes until browned. Flip them over, cover with a lid, and cook on low heat for 3–4 minutes until fully cooked.

Add the sake, mirin, and soy sauce to the pan and coat the rolls evenly.