Start by slicing the chicken breast in half. You don't want too thin slices, so cutting in half is enough.
Season the chicken with salt and black pepper to taste.
Coat the chicken in white flour.
In a big enough bowl (should fit the chicken breasts), add the egg and mix it with a fork so the white and yellow part are mixed. Add one chicken breast at a time, with the help of a fork. Make sure the whole chicken is coated in the egg.
In a bowl or plate, add the panko flour. Immediately after you place the chicken into the beaten egg mixture, place it into the panko flour plate. Coat it well.
In a large frying pan on medium-high heat, add the vegetable oil. Wait for the oil to be hot. Fry the chicken on each side until golden brown. It should take around 3 minutes per side. If you have a food thermometer, the inside of the chicken should be at 165°F.
Serve it on top of white rice. It also goes great with Japanese curry (Kare Taisu)