Cut each chicken thighs into 4 pieces. Prick the chicken with a fork so it can absorb more flavour.
Combine the teriyaki sauce ingredients in a medium bowl or sealable bag.
Add the chicken into the bowl and marinate for at least 2-3 hours in the fridge.
Heat the oil in a non-stick pan over medium-high heat and place the chicken pieces skin side down, SAVING the marinade (sauce). (Do not add any liquid so that chicken will brown).
When skin side has browned, flip the chicken and add the sake. Quickly cover the pan and cook over medium heat for 8-10 minutes.
Remove the chicken on to a plate and wipe off excess grease from the pan.
Heat the oil and put the chicken back in the pan, skin side down, and cook until the skin becomes crispy. Flip the chicken and pour in the remaining marinade/sauce into and cook until the sauce has reduced.
Use a spoon to pour the sauce over the chicken while cooking.
Transfer the chicken to a plate and drizzle the remaining sauce on top.