Bosch at first is Ryu's partner and "friend" in the Rangers, but later becomes one of the principal antagonists throughout the game. He comes from a rich family (he is the son of Vexacion, one of the Regents) and has been raised to fight in a manner similar to ancient Spartans (a particularly disturbing SOL sequence shows a prepubescent Bosch killing a Genic five times his size at the demand of his father). This means he possesses a great deal of both political and physical power.
Despite his high D-Ratio and prestigious family background, Bosch is stuck with the Rangers in the Low Sector's of Shelter trying to earn more recognition from the higher ups. He is partnered with Ryu whose good work ethic counters Bosch's selfishness and ambition.
Bosch is introduced to the player as being a caring friend to Ryu initially who is simply overwhelmed by the events that transpire, but the SOL system later reveals that Bosch's friendly demeanor is an act he puts on as he tries to politically wheel and deal his way to a higher station in society. Bosch is arrogant, selfish, cruel, and desperately seeks approval, stemming from his unorthodox childhood and his overbearing father. Bosch lacks the strength of will to simply wait and earn his recognition, instead he is constantly trying to find a shortcut to power. His defeats at the hands of Ryu greatly injure his pride and eventually leads to an obsession with killing Ryu. His obsession grows so strong he grafts the arm of Cheytre on to himself and allows the Dragon to consume and take over his body in hopes of defeating Ryu.
He fights Ryu a total of three times in the game, each time growing more and more obsessed with defeating his former partner. He has a D-Ratio of 1/64.
Bosch is only a temporary party member and doesn't learn any abilities other than the ones he starts out with. However, he is a formidable melee combatant while he is still in the party, having higher stats than Ryu across the board. His Field ability is the ability to kick, though it's only useful for engaging enemies.
Bosch is also one of the game's bosses, being fought a total of four times.