In a small bowl, bring together marinade ingredients: soy sauce, brown sugar, Mirin, rice vinegar, sesame oil, minced garlic and corn starch. Whisk to combine.
Marinade chicken tenderloin cubes in marinade for t least 4 hours and up to 24 hours. The longer it is marinade, the more flavorful the chicken will be!
Thread marinated cubed chicken, pineapple pieces and bell peppers onto skewers. Alternate between chicken and veggies, but feel free to use more of the items you like!
Fire up grill to medium high heat, then generously grease grill grids with cooking oil.
Place skewers onto grill grids, grill for 3-5 minutes on each side, or until chicken is fully cooked. If chicken starts to burn excessively, move it so that it is cooked under indirect heat. Chicken should have an internal temperature of 165℉ when fully cooked. Avoid undercooking or overcooking. Some slightly charring on the chicken is expected, even encouraged!
Remove from heat, garnish with green onions.
Serve and enjoy!