Full Metal Panic! Volume 5 by Shouji Gatou

On orders from Mithril, Sousuke has been forced to abandon Kaname to focus on learning the secrets the Arbalest and the lambda driver. Meanwhile, Kaname—left to the care of a remote and anonymous intelligence agent—feels the threat from a mysterious pursuer drawing ever closer. Their challenges will lead them both to the tension-racked streets of Hong Kong, a city even more divided than the burgeoning couple's destinies. And a series of climactic showdowns will bring them to a reckoning with enemies old and new!