A portion of an Ubisoft forum interview with Jason Vandenberghe, Creative Director...

JV: Throughout the game there are these “safehouses” – places where your allies have set up shop to set about the business of taking their home back from the villains who have turned it into a warzone. There are four types, each one related to a specific character and a specific kind of player ability.

One of these safehouses is controlled by your old teacher. However, he’s not 100% sure that you can be counted on – and you and he didn’t exactly get along before you left the last time, so he’s a tad reluctant to just hand over his entire stash of ancient Kusagari wisdom. That said, for a fee (using the gold you ‘recover’ from your enemies Smile), he’ll teach you new moves and unlock new abilities.