In a large skillet over medium high heat, add some oil and once hot, brown the chicken breasts on both sides for a few minutes.
Place the browned chicken breasts in the slow cooker.
In a small bowl, whisk together all the SAUCE ingredients.
Pour the SAUCE mixture over the chicken.
Cover and cook on HIGH for 4-5 hours or on LOW for 8 hours.
Remove the chicken from the slow cooker place it in a large bowl and shred with two forks.
Pour the teriyaki sauce from the slow cooker through a strainer into a saucepan and place on the stove over medium-high heat. Bring to a simmer.
In a small bowl, mix the cornstarch with the water until dissolved and add the slurry to the saucepan. Bring it to a boil and cook for 1-2 minutes or until the sauce has thickened.
Pour the sauce over the shredded chicken and toss to coat.
Serve with rice, sprinkle with sesame seeds and green onions.