Put kombu, wakame, black pepper, garlic, ginger, and mushrooms in a soup pot. Add soy sauce, water, and salt. Bring to a boil. Lower the heat and cook for 20 minutes.
Remove from the heat and let cool for about an hour.
Strain the mixture, but keep the solids aside; we will add them later; Pour the liquid back into the pot. Add pineapple cubes and miso, cover and bring to a boil; remove the lid and continue to cook on high heat until the liquid is reduced by about half.
Return the solids to the pot. Cover and leave in a cool place overnight; Then filter again and transfer the liquid to a bottle. Store in the fridge.