O-Parts Hunter Vol. 2 (manga)
The government of Stea is on the hunt for a pair of rogue O-Parts users. Armed with a high-class piece of weaponry, this devious pair of lawbreaking brothers is ready to hit Stea's special squad with everything they have. Will an even more powerful O.P.T. be able to stop their violence? Later, Jio's past comes into focus when more is revealed about the origin of his unique O-Part and the identity of his master: a powerful wolf named Zero!