Sanzokuou

Nagato [Seyu] 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 Nagato [Seyu] was only half-aware of. Everyone in the family line inherited a strange sword, a black katana that is much heavier than it looks and is only usable by people of Nagato's [Seyu's] bloodline. They also passed on a strange star-shaped mark on their chests, and as Nagato [Seyu] inherits the mark, the mark on his father's chest fades.

Soon after Nagato [Seyu] learns his family's secrets, his father is accused of treason and is taken away to a larger city. He follows them, carrying along his heavy heirloom. Eventually, Nagato [Seyu] finds that his father has been murdered, hence he sets out for revenge. Along the way, he meets a beautiful assassin named Natsume [ Megumi ] . What adventures could the future hold for these two?

Note:
The names in the [ ] are the names of the characters from the latest scanlated manga release of this series of the first 4 chapters.