I may have missed something, but is it possible for a character to learn a technique that he did not pick during character creation which he does not have access to after?

Ex. I made a character with the Daidoji Spymaster School (CoS p90) and the choice during character creation was to pick one from the Ninjutsu Techniques of 'Like a Ghost' or 'Skulk'. Since Ninjutsu isn't in the list of techniques available for the school, was wondering if/how the character can purchase the other ...

Thanks

Yi Xiao Nai He