Press the fried tofu with kitchen paper to remove excess oil, then cut into bite-sized pieces.

Cut the chicken breast in half lengthwise, then slice diagonally into bite-sized pieces. Place in a bowl and mix with sake, salt, pepper, and cornstarch.

Heat vegetable oil in a frying pan over medium heat. Add the chicken and cook until browned, flipping occasionally. Add the fried tofu and stir-fry briefly, then add the seasoning mixture and simmer until thickened.