|Height||1', 11" (at shoulders)|
|Faction||Imperial Army, State Section III, Courier|
|Debut||Episode 1 (anime)|
|Japanese Voice||Kazuki Ogawa (小川 一樹)|
|English Voice|| Smokey Delange (Episodes 1-4)|
George Manley (Episodes 7-on)
- Mercury is State Section III's Courier Private First Class messenger dog. He is a male Labrador retriever with a goofy face and a bad habit of biting people's heads (and refusing to let go). This is shown on page 124 of Volume 2 and episode 1 (Anime).
- He is able to sniff out drugs (supposedly; shown on page 130-131 of volume 2), and was in corrective training for some time. He usually is in the care of Sergeant Major Lili Stecchin, who doesn't look upon the dog as one of her subordinates (like Oland), but simply as a good friend. He is very fast, reliable and sensitive to the emotions of his team. He was demoted from Corporal to Courier Private First Class for biting an officer in Episode 1. Their reaction to a particularly unpleasant officer (Major Connery) led to the previously mentioned incident. He resembles a Labrador Retriever.
- While Mercury is normally seen as a friendly dog with the members of Section III, when events warrant it, he shows himself to be what the commoners referred to as a "military hound/army dog," and can even disarm opponents.