Way of the Samurai 3

First you must acquire all swords of this stance, which is the hard part and specific guides are made for it. There are roughly twenty for each, some easy to find others hard, but you definitely want to start collecting them in your sword storage which can be upgraded by a merchant at the Posting Station. Throw out any doubles that have lower stats than another.

Now either use them for a while to learn their moves (this would take forever) OR take them three at a time to Uepon the merchant at the Posting Station who sells the basic, advance and special scrolls AFTER DAY 5 (sleep for five days). Buy and use each of the scrolls while equipping each of your three swords until all their skills are learned, THEN MAKE SURE YOU KILL UEPON AND TAKE YOUR MONEY BACK, look for it, it is there. This is also easier on Insta-kill as he can run off the map with all your hard earned money then its gone for good). Once you get your money back leave Amana from the world map, start again sleeping for five days then rinsing and repeating for your next three swords.

You can tell if you have learned all of a weapons skills by looking at its details under weapons in pause menu. Once all skills from all swords of this stance type are learned the achievement pops.

If your short on cash there is a easy way to get the max amount of money fairly quickly. After day 5 buy all the scrolls you can from Uepon then sell them to the other merchant at the Posting Station, this may take a few trips depending on how much money you have, then return to Uepon and kill him to get your initial money back netting a good profit. The more money you spend on Uepon the more you make selling it all to the other merchant. Then leave Amana from the map to restart again until you have enough. As long as you do not leave the Posting Station or Amana from the map before killing Uepon he will continue to hold all money that you have used to buy from him which you of course want back.