My name is Sean Griffin and one day my wife, Ashley and I went to an anime convention. Me dressed as Monkey D. Luffy and her as Tashigi, when we came across the Merchant. He gave us two swords, one Zoro's and the other Tashigi's, for free.
In hindsight, we probably should have been suspicious that he was giving them away without charging us, but we didn't want to pass the offer up. Now we find ourselves in a place called Equestria, that was from a show that my wife watched called My Little Pony: Friendship is Magic. The only thing is, these ponies were anthropomorphic instead of normal ponies. We were also changed into the characters we were cosplaying as. Oh, and if that wasn't enough, we arrived in Canterlot while it was being invaded!
Warning: there will, obviously, be spoilers for the anime and manga, so if you haven't gotten very far and you don't want to be spoiled, you should watch and/or read it first.