O-Parts Hunter, Vol. 2 — Seishi Kishimoto

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!