Cut cucumbers into long, thin noodle shapes using a spiralizer set to the thinnest setting.
Place cucumber noodles in a fine-mesh strainer set over a bowl. Sprinkle with 1/2 teaspoon salt and toss until combined. Let cucumber stand until moisture is drawn out, about 30 minutes.
Whisk rice vinegar, sesame oil, soy sauce, and sugar together in a bowl until sugar is dissolved. Add cucumber; toss gently until coated. Season with remaining 1/2 teaspoon salt; sprinkle with sesame seeds.