Mix together soy sauce, sake, mirin, honey, and ginger in a small bowl.
Cut open the thick part of the chicken breast to even out the thickness.
With a fork, puncture the chicken breast all over. Using a butcher’s twine (cooking string), roll, wrap, and tie up the breast.
Heat oil on a frying pan, grilling both sides of the breast. This is to trap in the umami flavor.
Put together chicken breast and the marinade from Step 1 inside a Ziploc bag. Close the bag while keeping the air out. The bag should be airtight.
Place the bag inside the rice cooker and add in hot water to cover. The hot water should be enough to cover the chicken. The recommended temperature is below 158°F (70°C).
Close the lid, and keep warm for 2 hours.
Take the bag out of the rice cooker and let cool. Once it is cooled down, slice the chicken and the chashu is ready!*Please use a Ziploc bag that's able to handle 158°F (70°C).*Please make sure the rice cooker you are using is compatible for slow cooking with items such as Ziploc bag.