Soak wooden skewers in water for 10–20 minutes to prevent burning while grilling.

In a medium bowl, combine soy sauce, water, red wine or mirin, brown sugar, and vinegar. Whisk until the sugar dissolves.

In a large bowl, mix minced garlic, ginger, and ground pepper. Add 1/4 cup of reserved marinade and then chicken, coating well.

Transfer remaining marinade to a saucepan and bring to a gentle boil. Mix cornstarch with water, then stir into sauce until thickened.

Thread marinated chicken onto soaked skewers, 3-4 pieces per skewer.

Preheat grill to medium-high (400°F / 200°C). Grill skewers for 8–12 minutes, turning occasionally and basting with thickened sauce.

Let skewers rest for a few minutes before serving. Drizzle leftover sauce over skewers.