Cut into the thick part of the chicken breast and flatten it to about 1cm thickness using a rolling pin. Place it in a plastic bag, add sake, sugar, and salt, and massage well. Let it rest in the refrigerator for 10 minutes.

Cut the nira into 5mm pieces and finely chop the umeboshi after removing the seed. Mix them in a bowl with ponzu soy sauce, sesame oil, and white sesame seeds to make the ume-nira sauce.

Add potato starch to the plastic bag with the chicken and coat it evenly.

Heat salad oil in a frying pan to 170°C. Fry the chicken for about 3 minutes until golden brown, then flip and fry for another 2 minutes until cooked through and crispy.