Nagakado was a fairly normal boy, albeit a trap genius. He and his father lived comfortably in a small town. However, that innocent family had secrets that Nagakado was only half-aware of. Everyone in the family line interited a strange sword, a black katana that is much heavier than it looks and is only usable by people of Nagakado's bloodline. They also passed on a strange star-shaped mark on their chests, and as Nagakado inherits the mark, the mark on his father's chest fades.