Two people met at the crossroads of Chinatown: Inumi Haserou, a high school student who worked as a bodyguard for a fee of 1000 yen per trouble, and Nata, a girl who called herself a Sage and mysteriously collapsed in a nearby alley. Haserou decided to protect Nata, but their lives quickly turned chaotic when a group of vampire-like beings known as "Demonic Sage" started attacking them, feeding on people's Ki energy. They were after Nata, who possessed a powerful weapon that could make the creatures powerless. Haserou had to face this sudden and perilous upheaval in his once peaceful life.