1. Wash the chicken and pat dry with paper towel. Cut the chicken thigh into 3-4 pieces. (about 1.5 inch pieces). In a medium size bowl, add all seasoning ingredients, ginger, garlic, sake, sesame oil, salt and tsuyu with chicken. Rest it in the fridge for about 30 to 60 mins.
2. Pour beaten egg into the mixture and stir them to combine well. In a separate medium bowl, mix the rice flour and katakuriko (potato starch), and set aside.
3. Bring the oil in deep frying pan or a wok to 160C.
4. Dredge marinated chicken pieces with flour mixture and dust off excess flour from the chicken.
Deep fry them for about 4 minutes (a few chicken in several batches.) and transfer the chicken onto the paper towel lined plate. Let them sit for the moment, the chicken will continue cooking with the remaining heat. Continue to deep-fry the remaining chicken.
5. When you deep-fry all the chicken pieces, then bring the oil to 180 C. Deep fry them for the second time for about 1 to 2 mins, or until a deep golden brown and crispy.