Arm of Kannon

Arm of Kannon, originally titled Birth (バース, Bāsu) in Japan, is a manga by Masakazu Yamaguchi. The series was licensed in English by Tokyopop; the Tokyopop version of the manga went out of print as of August 31, 2009.

Plot
Sixteen-year-old Mao and his older sister Maya haven’t seen their father since his disappearance three years ago. One day, their father unexpectedly returns home with the Arm of Kannon, a cursed Buddhist artifact, which could bring about the end of humanity. Mao, Maya, and a mysterious swordsman that has emerged to protect them must try to stop the government from obtaining the Arm of Kannon and using it to create super-soldiers for the military.