Cook the rice: Cook the sushi rice according to package instructions, then season with rice vinegar and maple syrup. Let it cool to room temperature.
Cook the chicken: While the rice is cooling, heat olive oil in a skillet over medium heat. Season the chicken with a pinch of salt and pepper, then cook for 6-7 minutes per side until fully cooked. Let the chicken rest for a few minutes before slicing it into strips.
Prepare the musubi: Cut the nori sheet into strips (about 2–3 strips per musubi). Lay a strip of nori flat on a clean surface. Spoon a portion of cooled rice (about 1/4 cup) onto the nori. Gently press the rice down with your fingers to compact it, then place a few slices of chicken on top.
Shape the musubi: Carefully fold the nori around the rice and chicken to form a small, neat package. If needed, use a musubi mold or press to help shape the musubi.
Serve: Repeat the process for the remaining musubi. Sprinkle with sesame seeds if desired.