How to Make It
Soak 8 (12-inch) wooden skewers in water 15 minutes.
Stir together 1/4 cup cilantro, soy sauce, sesame oil, honey, sesame seeds, and black pepper in a large bowl. Reserve half of marinade. Add tuna to remaining marinade in bowl; toss to coat. Chill 15 minutes.
Remove tuna from marinade. Place marinade in a saucepan; boil 2 minutes. Thread tuna, shishito peppers, mushrooms, and eggplant onto skewers, beginning and ending with tuna.
Heat a grill pan over medium-high. Coat with cooking spray. Grill skewers until charred, 3 to 4 minutes, turning once. Brush with cooked marinade during last minute of grilling. Place skewers on a plate. Top with reserved marinade and remaining 1/4 cup cilantro.