Trim the tentacles off the calamari tubes, then cut the tubes into 1/4-inch rings. Trim tentacles, keep only what is needed. Set aside.
Whisk together the lemon juice, soy sauce, Mirin, oyster sauce, rice wine vinegar, and grated ginger. Set aside.
Grind the peppers in a mortar and pestle or a spice grinder. Place them in a large plastic bag and add salt and cornstarch. Shake the bag to mix the ingredients.
Heat 1/2-inch of oil in a large shallow skillet.
Add the calamari pieces to the plastic bag with the salt and pepper and shake to coat well.
Carefully drop the calamari pieces into to the hot oil and fry till golden. You may want to do this in batches; the calamari shouldn’t be crowded in the pot.
When golden, remove calamari with a slotted spoon and drain them on several layers of paper towels.
Toss the mizuna with half the dressing, and divide among four plates.
Top each salad with a quarter of the fried calamari and drizzle with the remaining dressing.