I've seen that hidden dagger in a movie before. It was one of the Sho Kosugi ninja movies. I forgot which one. This looks like it might be based on that sword.
Six hundred dollars?!? Ain't no way. Also, I'd be worried about carrying it and the dagger vibrating loose and falling out onto my leg or heel. It's cool, don't get me wrong, but kind of gimmicky and unsafe. I'd rather get just the ninjato for a couple hundred less and then buy a tanto or knife of my own choosing separate. The Hanwei Iga ninjato would be my choice instead.