Press the “saute” button on the Instant Pot. Add a little oil, followed by the pork belly. Brown the pork belly on all sides. This should take about 5 minutes.
Remove the browned pork belly to a plate and set aside.
Add more oil to the Instant Pot and add the ginger and garlic. Saute until fragrant and golden.
Then add the water, soy sauce, sake, brown sugar, and mirin. Use a wooden spoon to deglaze / scrape up any browned bits stuck to the bottom of the pot. Note: This step is important. If you have browned bits left on the bottom of the pot, the Instant Pot will display a “burn” message and stop cooking. Press the “cancel” button to stop the sautéing.
Then add the pork belly back into the pot. Give it a stir so that everything is evenly mixed. Put the lid back on.
Cook on “high pressure” for 30 minutes. Then do a "natural pressure release" for 15 minutes.
Remove the lid, and press the “cancel” button. Then press the “saute” button. Leave the lid off and let the sauce bubble away and reduce until it becomes thick and glaze-y. Stir frequently to prevent sticking / burning.
Pour the pork out into a bowl, and serve hot, with rice. Enjoy!