Slice the cucumbers into thin rounds, about ⅛-inch thick. A mandolin slicer works great for uniform pieces.
2 Japanese cucumbers
Salt the cucumbers by tossing them in a bowl with ½ teaspoon salt. Let sit for 10 minutes to draw out excess moisture.
1/2 teaspoon salt
Drain and squeeze the cucumbers. Either use a clean towel to press gently or place in a mesh strainer and press with the back of a spoon.
Make the dressing by whisking rice vinegar, sugar, soy sauce, and sesame oil in a small bowl until the sugar dissolves. You can also use simple syrup or honey.
2 tablespoons rice vinegar, ¾ tablespoon sugar, 1 teaspoon soy sauce, 1 teaspoon toasted sesame oil
Rehydrate wakame (if using) by soaking in warm water for 5 minutes, then draining and squeezing dry.
1 tablespoon dried wakame
Toss cucumbers and wakame with the dressing until fully coated.
Top with toasted sesame seeds just before serving.
¾ tablespoon toasted sesame seeds
Chill for 15 minutes before serving.