Steam or blanch the edamame beans until tender, then rinse them under cold water. Drain and put them in a bowl.
Cut the cucumber in half lengthwise, then scoop out the soft flesh. Slice these into half-moon shapes, then cut them in half. Add these to the beans.
Thinly slice the spring onions, then add to the beans.
Add the soy sauce, rice wine vinegar, Mirin and sesame oil to the salad. Toss gently. Taste and adjust it to your liking - you can add some lime juice too.
Scatter the sesame seeds on top of the salad then serve.