This is a little tricky to explain. Wikipedia tells us, "Kakuni is made of thick cubes of pork belly simmered in dashi (Japanese soup stock), soy sauce, mirin (a kind of rice wine), sugar and sake. By cooking it for a long time over a low temperature, the collagen breaks-down into gelatin, keeping the meat moist while becoming extremely tender, allowing it to be consumed with chopsticks easily." So there we go. Tasted great.