Step 1Heat a grill or grill pan over medium-high heat. Rinse and dry the chicken thighs. Season with salt and pepper. Set aside.
Step 2Combine the ponzu, lime juice, ginger, garlic, chile and sugar in a small saucepan. Cook over medium heat, stirring, just until the sugar dissolves, about 2 minutes.
Step 3Place the chicken, skin side down, on the grill. Brush the top of the chicken with the ponzu mixture. Turn the chicken over every 2 minutes or so, brushing with the sauce every time until the chicken is cooked through, about 10 minutes.