Make the sauce: Combine soy sauce, honey, rice vinegar, sesame oil, garlic, and ginger in a saucepan. Warm until the honey dissolves.
Thicken: Mix cornstarch with cold water. Whisk it into the sauce and simmer for 2 to 3 minutes. Cool completely.
Marinate: Reserve half the sauce. Toss the chicken with the remaining sauce, cover, and refrigerate for at least 30 minutes.
Assemble: Thread chicken, bell pepper, and onion onto soaked skewers, leaving small spaces between pieces.
Grill: Cook over medium-high heat for 10 to 14 minutes, turning every 3 to 4 minutes. Baste near the end.
Or bake: Bake at 220°C for 18 to 22 minutes, turning halfway. Broil briefly for extra caramelization if desired.
Check and serve: Cook until the thickest chicken piece reaches 74°C. Rest for 5 minutes and garnish with sesame seeds and green onions.