This reacting can be part of the patina forming process, but not necessarily. Certain foods may react w/ the steel and not develop a patina. I have a Moritaka kiri-gyuto that is clad. The cladding on that knife reacts horribly w/ many foods, rusts easily, and won't take a patina at all.
I don't have a Kono, but I have a Yusuke in white #2 - it may be the same steel, or something very similar - and I find it to be not terribly reactive or prone to rust. When I cut citrus fruits, I often rub the blade down w/ a spent half of a lime and let it sit for a while; no problems w/ rust and it get a good patina. Patina will also change with use depending on what you're cutting.