Position a rack in the center of the oven and heat the oven to 375°F. Line a large rimmed baking sheet with foil and spray with cooking spray.
Combine the soy sauce, brown sugar, orange juice, ginger, sesame oil, and garlic in a 1-quart saucepan and bring to a boil over medium-high heat. Immediately remove from the heat and let cool. Stir in the scallions.
Heat the oil in a 12-inch skillet over medium-high heat until shimmering hot. Sear the chicken until golden-brown, about 4 minutes per side.
Transfer the chicken to the baking sheet and drizzle with one-third of the teriyaki sauce. Layer the starfruit over the chicken, overlapping the slices slightly. Drizzle with half of the remaining teriyaki sauce.
Bake the chicken until an instant-read thermometer inserted in the thickest part of a breast registers 165°F, about 15 minutes. Remove the chicken from the oven and turn on the broiler. Drizzle the chicken with the remaining teriyaki sauce and broil until the starfruit just begins to caramelize, about 5 minutes.
Transfer the chicken to serving plates. Carefully pour the teriyaki sauce from the baking sheet into a small pitcher and drizzle some over the chicken. Garnish the chicken with the cilantro and sesame seeds and serve, passing the remaining sauce on the side.