Knife is rusting after using it only twice I recently got a knife as a gift and after only using it two times it has started to rust, despite making sure to properly clean it and dry it after using it. There is also one large spot of black/blue discolouration on the back of the knife. Also I'm not sure if this helps but the branding on the knife says 'Okeya'. How can I avoid this happening and what should I do to treat the rust?
A list of methods for removing rust from knives can be found at Knife Depot.  In your case, as the rust appears very light and is recent, simply wiping with a vinegar cloth may be sufficient (possibly also needing a wipe with fine steel wool) and then wipe off any remaining vinegar.

In future, it is imperative that you dry the washed knife immediately and then apply a very thin coating of food safe (e.g., vegetable) oil (or fat) - wipe on then wipe off.  Also, don't leave the knife wet (e.g., while using it) for any length of time - wipe with a dry cloth.