There is no doubt that when you think Japan you think of shoyu. The fact is fermentation of foods is one of the keys to extracting flavors and here I use kombu to extract umami.
Whenever you cook you need to consider flavor /as a key/ and the raw materials you intend to use and how best use them. This is the beauty of cuisine, the pathway of flavor is what makes a chef begin to discover his own taste palate.
Note: I always explain that the kitchen is based on time, temperature and pressure – so find the balance.