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"Didn't your mommy taught you? If you meet such a scary person, take care about the hole of your wallet and a**"
―Gates rambling, right before slaughtering the Balic's militia forces.

Gates is the primary antagonist in Full Metal Panic! The Second Raid.

An Amalgam agent and the head of Amalgam's Execution Squads, Gates's antics make him ferocious and relentless, but highly unreliable when it comes to more professional contracts. He is known to kill or punish his subordinates for the slightest of reasons. Gates kills through a variety of methods including shooting an Amalgam commando in the head when he back talked and crushing Xia Yu Fan's Shadow Arms Slave with extreme ferocity. He is also shown to be highly abusive of his subordinates with him kicking his second in command off a helicopter and nearly drowning him in a pool.

Despite such brutality, Gates showed his intelligence by being able to deduce accurately the tactics that Mithril's Special Response Team utilized in their intervention of the Balic civil war. One light side about Gates is that he is protective about himself, especially about being bald since the front of his head shows no hair present.

It can be assumed that Gates was known as "Mr. Kalium" throughout Amalgam, as in the light novel, A Dancing Very Merry Christmas. It is said that Gauron (otherwise known as Mr. Iron) was responsible for the death of Mr. Kalium. Gauron does put into motion a series of events that end with Gates's death, though Gauron's only intention seems to have been to lure Sousuke to himself.

It is shown that he is also a sexual deviant. mocking and abusing Xia Yu Lan (especially) and Xia Yu Fan, although were underage he did not hold back to "satisfying" them as well as himself leading him to being a pedophile. He also calls them Lolita-chan (lolita is a unofficial term for a child in pornography) when taunting them for escaping. When he manages to acquire the body one of the girls it makes references to the idea that he will dabble in a spot of necrophilia with either or both of the girls bodies. In the same scene where he finds out that the girls have escaped, it depicts him being interrupted in the process of masturbating over the image of kittens on his wide screen TV. A truly twisted individual, that when concluding his communication with Xia Yu Lan and Xia Yu via his television he returns to his previous channel which is now depicting squirrels. It would seem that on top of pedophilia he has a penchant for bestiality, at least so far with small "cute" mammals. Gates can speak some Mandarin aside from English. Apart from his complete immorality, Gates showed symptoms of the experimental drug TI-971, such as violent outburst and loss of memory. This dangerous drug used by the previous terrorist group A-21 was used in order to develop the brain zone that impulses the Lambda Driver.

Gates was killed by Sousuke in Hong Kong during Xia Yu Fan's killing spree, when he uses the Arbalest's Lambda Driver in full power to defeat his Codarl Arm Slave. He and his entire squad were completely decimated by the Mithril's agent. Like Gauron, Gates was a pilot of the Plan-1058 Codarl-i, with diferent equipment such as dual machine gun and a personal monomolecular cutter that used for penetrating into Xia Yu Fan Venom's cockpit, such weapons were destroyed by a shot of the Arbalest's 2x XM 18 Wire Gun.

It was showed by an Amalgam agent that Gates had the high ground in the organization, being assigned commander and rivaling with Leonard Testarossa, which he seems to despise. Gauron could've easily got his post, but since he was a freelance mercenary, never compromised and put operations at risk only for getting to Sousuke, Amalgam decided to give the rank to Gates.