Add pork belly to a large pot so the pork can lay flat. Add cold water so the meat is submerged and turn the heat to high.
Add sliced ginger and bring to a boil. Once the water comes to a boil, reduce to a simmer. Continue to simmer for 1.5 – 2 hours or until the pork is tender. If the water reduces and the pork is not submerged, add more water.
Using tongs or a wire strainer, gently remove the pork from the pot.
Gently rinse the pork belly with cold water being careful not to break them.
Cut the pork into 3-4 equal pieces, about 1.5” wide.
Add the water, shoyu, sake, sugar and pork belly to another pot and turn the heat to high.
Once the liquid boils and the sugar dissolves, reduce heat to a low simmer and cook for 15-20 minutes or until the sauce has reduced to about 1-2 tablespoons.
Use a spoon to baste the pork with the sauce so all sides of the meat gets coated.