Rehydrate wakame: Soak dried wakame in a bowl of water for 10 minutes. The wakame will expand a lot.
Sweat cucumbers: Use a mandoline slicer to thinly slice the cucumber. Toss the cucumber slices with salt and set aside for 10 minutes. The salt will draw water out from the cucumbers as they sit.
Make dressing: Mix together green onions, ginger, soy sauce, and sesame oil.
Drain cucumbers: Drain the water that was released from the cucumbers. Take a handful of cucumber slices and gently squeeze out excess water. Repeat for all the cucumber slices.
Drain wakame: Once the wakame has expanded, drain the water out of the bowl. Take a handful of wakame pieces and squeeze out excess water. Repeat for all of the wakame.
Assemble salad: Place cucumber slices on the bottom of a shallow bowl. Top with tofu and wakame and pour green onion dressing all over. Sprinkle sesame seeds on top and gently mix.