Prep the chicken: Trim any excess fat from the chicken thighs. Pat dry with paper towels for better texture.
Mix the sauce: In a bowl, whisk soy sauce, honey, brown sugar, rice vinegar, mirin, garlic, ginger, sesame oil, and chicken broth until smooth.
Load the slow cooker: Place the chicken in the slow cooker in an even layer.
Pour the sauce over the top, making sure all pieces are coated.
Cook low and slow: Cover and cook on Low for 4–5 hours or on High for 2.5–3 hours, until the chicken is tender but not falling apart.
Shred or slice: Transfer the chicken to a cutting board. Shred with two forks or slice into bite-size pieces.
Thicken the sauce: Turn the slow cooker to High. Whisk cornstarch and water into a smooth slurry.
Stir it into the sauce, cover, and cook for 10–15 minutes until thick and glossy.
Combine: Return the chicken to the slow cooker and toss to coat in the sticky sauce.
Finish and serve: Sprinkle with sesame seeds and green onions. Serve over rice with veggies on the side. Add red pepper flakes if you want heat.