Slice cucumbers into large bite-sized pieces. Place in a sealable (Ziplock) bag or a plastic container that can be tightly, and securely sealed. In a small bowl, combine soy sauce, rice vinegar and sesame oil and mix well. Add dried red chili pepper slices for some heat. Pour the mixture over the cucumber pieces and shake the bag or tupperware until the cucumbers are well-coated. Refrigerate for 1 - 2 hours, periodically mixing the cucumbers to ensure the pieces are evenly coated. The meat of the cucumber will begin to absorb the color of the soy sauce, at which point, they should be ready to eat. NOTE: If you keep your chyuka kyuri no tsukemono in the marinade for 4 - 5 days in the fridge, they will begin to shrivel and they will likely become very salty. I prefer to eat mine the same day that I make them, or within a day or two of making them at the most. You also have the option to discard the marinade once your chyuka kyuri no tsukemono reaches the desired flavor that suits your palate. This will prevent the cucumbers from becoming too salty.