Make the cucumber-edamame salad: In a medium bowl, whisk together the soy sauce, rice vinegar, sugar, sesame oil, and optional 1/2 teaspoon sriracha until the sugar dissolves. Add the diced cucumber, cooked edamame, sliced scallions, and grated ginger; toss to combine and let sit at room temperature while you prepare the rest of the meal.
Prepare the sriracha mayo: In a small bowl, stir together 1/2 cup mayonnaise and 2 tablespoons sriracha until smooth. Taste and adjust heat, then set aside.
Flatten and season the chicken: Use the palm of your hand to flatten each chicken tender to about 1/4-inch thickness. Trim any visible tendons with kitchen shears. Season both sides of the tenders with 3/4 teaspoon salt.
Set up the breading station: Place the flour in one shallow bowl, beaten eggs in a second, and panko breadcrumbs in a third. Dredge each seasoned tender first in flour (shake off excess), then in the beaten eggs, then coat thoroughly with panko, pressing the crumbs to adhere. Transfer breaded tenders to a plate.
Cook the chicken: Pour enough vegetable oil into a large nonstick skillet to reach about 1/8-inch depth and heat over medium. When hot, add chicken in a single layer (cook in batches if needed) and fry until golden and cooked through, about 2 to 3 minutes per side. Transfer to a paper towel–lined plate to drain.
Assemble the bowls: Divide the cooked rice among 4 bowls. Dice the avocado and gently fold it into the cucumber-edamame salad right before serving. Slice the chicken if desired and arrange on top of the rice. Add a generous spoonful of the cucumber salad beside the chicken (not directly on the breading). Drizzle sriracha mayo over the chicken and rice, sprinkle with sesame seeds if using, and serve immediately, passing extra salad and sauce at the table.
