It's listed in the preorders on GAME here for only £14.99, listed as "Ninja vs Samurai" - which is its sub-title. I placed an order today.
I quite like the Kengo games. They may not be so great in the way people normally rate games, but they have a very "authentic" feel to them that I like. There's the singular focussed goal of becoming the best swordsman, there's the emphasis on learning your moves and strategising with them, and the patience and skill needed to win and move forward.