In a medium bowl, whisk together the ketchup, brown sugar, low-sodium tamari, rice vinegar, toasted sesame oil, and red pepper flakes until well combined.

Heat a skillet over medium-low heat and add olive oil. Sauté the shallots for 3–4 minutes until tender and translucent, then add minced garlic and ginger paste for another minute.

Pour the sauce mixture from Step 1 into the skillet with the sautéed aromatics and simmer on low heat for 8–10 minutes.

In a large bowl, toss the boneless chicken breast halves with half of the cooled sauce, ensuring each piece is well coated.

Preheat the grill to medium-high heat (around 400℉) and grease the grates with olive oil.

Thread marinated chicken pieces onto soaked skewers, leaving space between each piece. Grill for 5–7 minutes.

Turn skewers with tongs, baste with reserved sauce, cover, and cook for another 4–5 minutes, checking for doneness.

Remove from the grill, let rest for a few minutes, and serve drizzled with remaining sauce.