Combine pineapple juice and cornstarch in a small bowl, whisking until there are no lumps.
In a small saucepan over medium-high heat, add remaining marinade ingredients along with the cornstarch and pineapple juice mixture. Bring sauce to a simmer, stirring frequently.
Once simmering, reduce heat to medium-low and cook until sauce lightly thickens. Once sauce has thickened up, remove from heat and allow it to cool for several minutes.
Once the sauce has cooled, place cubed chicken in a large ziplock bag. Pour half of the sauce over the chicken and gently massage to coat the chicken.
Let chicken marinate in the fridge for at least 30 minutes. Place the remaining sauce aside for later.
When the chicken is done marinating, evenly divide the cubed chicken between skewers and heat a lightly oiled grill to medium heat.
Once the grill is hot, place skewers on grill. Turn the skewers every 3-4 minutes until the chicken is cooked through and the internal temperature reaches 165 degrees, about 16-20 minutes. During the last few turns, brush the chicken skewers with remaining teriyaki sauce.
Remove skewers from grill. Serve with chopped green onion and a sprinkle of sesame seeds.