Add the ginger, garlic, soy sauce, sake and sugar to a bowl and whisk to combine.
Add the chicken, then stir to coat evenly.
Cover and refrigerate for at least 1 hour.
Add 1 inch of vegetable oil to a heavy bottomed pot and heat until the oil reaches 360 degrees F.
Add the potato starch to the chicken to the and mix to coat each piece evenly.
Fry the chicken in batches until the exterior is a medium brown and the chicken is cooked through.
Drain fried chicken on a paper towel.
If you want the chicken to stay crispy longer, you can fry the chicken a second time, until it's a darker color after it's cooled off once.