Caravan Kidd Vol.1 - Vol.3

Caravan Kidd is a shonen science fiction manga by Johji Manabe. It was published in the United States and Canada in English by Dark Horse Comics.
Wataru and his partner Babo, two black market merchants with no morals to speak of, get caught up in a battle between the Helgebard Empire and the mysterious girl Mian Toris. To reward Wataru for saving her life, Mian collars both Wataru and Babo and declares them to be her pets. While dragging them across the continent, they learn that Mian's destination is a head-on confrontation with Shion, the empress of the Helgebard Empire itself, at Kyuraweil Keep.