Whisk together the soy sauce, mirin, honey, brown sugar, and ginger.
Add in the water and minced garlic, then whisk again to combine.
Pat dry the chicken thighs and add to a large bowl.
Pour the marinade all over the chicken thighs, ensuring that all of the pieces of chicken are coated. Cover the bowl and let marinade in the fridge for 2 hours, or overnight.
Preheat your grill and turn the heat to a medium high heat. Place the chicken on the grill and cook for 4-5 minutes.
Cover the grill, then reopen and flip the chicken, cooking for an additional 4-5 minutes. The chicken is done when the internal temperature reaches 160º
Notes
Marinade the chicken before grilling. The marinade is poured over the chicken and let sit either overnight if you have time, or at least 2 hours prior to grilling.USE A THERMOMETER! A thermometer really is the most reliable tool to help make sure your protein is finished cooking thoroughly.