[blackadder]

The rules of the Hikaribito dictate that the loser of a fight between them would become the winner's underling or specifically Shatei (basically means younger brother in yakuza terminology). See here:
http://en.wiktionary.org/wiki/shatei

Gou is pretty much the anti-Kouga in term of personality. I'm really liking the series so far, the two recent collaboration between Inoue and Amemiya have been really good. It's cool to see the CM for Sword Gai, the collaboration manga between the two in the Gouraigan's commercial.