Kombu is a Japanese kelp or brown seaweed. You could substitute a tablespoon or so of other seaweed, such as hijiki or wakame, or sprinkle a bit of salt on the radishes before cooking.

1 piece kombu (3-inch), soaked until tender and thinly sliced
2 c sliced radishes (or what you have)
generous pinch of chili powder or cayenne
water
2 c packed mustard greens or radish greens, chopped
soy sauce, to taste
orange juice, or other tangy fruit juice (optional)

1. Place kombu pieces on the bottom of a deep skillet or pot. Arrange sliced radishes on top (if using salt instead of seaweed, sprinkle it over the radishes now). Sprinkle with chili powder and add a small amount of water, gently, to just cover the bottom of the pan. Bring to the boil, reduce heat and cover. Let simmer until radishes are just tender, about 5 minutes.

2. Add greens to pan, season very lightly with soy sauce, recover and steam for just a couple of minutes, so that the greens are bright green. RemoveĀ  vegetables from skillet or pot and transfer to a serving bowl. Drizzle with orange juice and toss to mix ingredients.