Make the cucumber salsa first. In a bowl, combine cucumber, soy sauce, vinegar, scallions, and cilantro, and mix well. Cover and set aside.
To make the sauce, in a medium saucepan over low heat, stir together the soy sauce, vinegar, sugar, and wine. Stir frequently until the sugar is completely dissolved, about 3 minutes. Pour the sauce into a small bowl and set aside.
Dredge the fish in the flour. Heat a skillet on medium-high until hot. Add the olive oil and heat until hot but not smoking. Saute the fish for 2½ minutes on each side, until browned. Reduce the heat to medium, then pour in the sauce mixture and cover with a lid. Cook until the fish is cooked through, about 5 to 6 minutes.
Place the fillets on a platter, and pour the pan juices over the top. Serve immediately with a sprinkling of sesame seeds and the salsa on the side.
Notes
You can make the salsa the day before and store in the refrigerator.