It's a "hidden technique" which I learned from the book containing techniques passed down from generation to generation from my clan. This is the only technique written in a book whilst the others are passed down orally but since my character was only a kid he never had the chance to learn even a single one, with what happened and all. But even the book requires a hidden technique of it's own to be read which is only passed orally(else what's the point) and he learned this from his geno-sensei which in turn learned it from my character's father(because sensei is not part of the clan but was considered a brother to my char's father). I would also like to add a sword "secret technique" that he learned from geno-sensei himself while in his run from the Hidden Mist assassins.[@Halvtand]