Oil from the seeds of Camellia oleifera (same family as Camellia and tea) is the traditional Japanese choice for protecting tools from rust: use it when cleaning, and as a regular protective coating. Leaves a lovely deep, non-oily finish, and it's odourless and tasteless (handy for kitchen knives, but don't try drinking it.)
Cold pressed Camellia seeds blended with white mineral oil. Not for human consumption.
Niwaki Tip: The real trick with caring for your tools is to do it - it doesn't really matter exactly what, just get on with it.