Whisk together teriyaki sauce, pineapple juice, soy sauce, brown sugar, minced garlic, grated ginger, and sesame oil in a medium bowl until the sugar completely dissolves and the marinade looks smooth.

Place chicken in a large zip-top bag or shallow dish, pour the marinade over it, seal tightly, and refrigerate for at least 2 hours or up to overnight. Flip the bag once halfway through marinating to ensure even coating.

Preheat your grill or grill pan to medium-high heat (about 400°F). Remove chicken from marinade and reserve every drop of that leftover marinade. Grill chicken for 6-7 minutes per side until the internal temperature reaches 165°F and you see caramelized grill marks forming. Let chicken rest for 3-5 minutes.

While the chicken grills, add pineapple rings directly to the grill and cook for 2-3 minutes per side until they're beautifully caramelized with light char marks.

Pour the reserved marinade into a small saucepan and bring to a rolling boil, then reduce to a simmer. Cook for 5-6 minutes, stirring occasionally, until it thickens into a coating-consistency glaze that clings to the back of a spoon.

To assemble, spoon about 1/2 cup cooked rice onto each plate, layer with one piece of grilled chicken, top with a grilled pineapple ring, then drizzle generously with the warm glaze. Finish with a sprinkle of green onions and sesame seeds.