In a small bowl, combine the soy sauce, vinegar, lemon juice, sugar, and oil. Set aside.
Bring a pot of salted water to a boil and cook the soba noodles until just tender, about 3 to 4 minutes.
Drain the noodles and rinse under cold water until they are cool. Drain well.
In a large bowl, combine the noodles, scallions, cucumber, and slaw and toss with the dressing. Serve at room temperature or chilled.