Stainless-clad blades, including your Anryu, only have a small portion of carbon steel exposed, and yes, it is closest to the cutting edge. This exposed carbon steel will react with water, foods, humid air, etc., and discolor in the process... this oxidation creates a protective shield on the steel known as patina.
When it is dull grey, iridescent blue, black... it's all good development; it's when it starts getting orange-y that you need to concern yourself as it's indicative of rusting which happens when the blade is left with reactive items on it for too long. This can usually be scrubbed off with abrasive powder, and unless left for a long long time, it is usually a non-issue. Even when left for awhile it can be rectified. Here's an example of a rusted blade that had a decade of ignored years; it pitted, but I got most of it out: http://www.chefknivestogoforum.com/viewtopic.php?f=2&t=1281&hilit=kanji%20id
Patina is good... in my book. It reduces the reactivity you experience with foods like melons, peppers, strawberries, onions, etc. Many are of the opinion that patina is a disgrace... based on the prim & proper paradigm of Japanese culture. It's a personal choice. You can constantly polish off the patina, but to me... it's a nonsensical logic.