Put a large skillet or a wok over medium-high heat and brush it with a little oil. When the pan is hot, add the zucchini slices in 1 layer and cook until they are lightly browned, about 1 minute. Turn them over and cook for another minute. Remove them to a plate.
Brush the pan with some more oil and add the onions, squash, scallion whites, ginger, and chile pepper. Give them a good stir and cook until they begin to soften, about 3 to 4 minutes. Add 2 tablespoons of soy sauce and 1 tablespoon rice wine vinegar. Add the edamame, cook for another minute. Remove them to another plate.
Brush the pan with some more oil and add the mushrooms and garlic. Cook until the mushrooms start to release their juices and add 1 tablespoon of soy sauce. Cook until most of the liquid has evaporated and remove them to a plate.
Carefully wipe out the pan and brush it with some more oil. Add the scallops and cook them until they are nicely browned on both sides, about 1 to 2 minutes per side. Add the sake and cover the pan to steam the scallops and cook them through, about another 2 to 3 minutes.
To serve: Divide the zucchini and lay them across each of 2 plates in a neat diagonal row. Divide the squash edamame mixture into 2 even, neat piles on the zucchini. Cut the scallops in half horizontally to make 2 even rounds. Lean the scallops seared sides up on the pile of the squash edamame mixture. Top each pile with a piece of mushroom. Garnish with the scallion greens and drizzle with the remaining soy sauce and rice wine vinegar.