Kaname Chidori is an average high school student, living her own life until a new transfer student comes (Sousuke Sagara). For some reason, Sousuke decides to stick with Kaname and follow her everywhere.
One thing Kaname does not know is that Sousuke is a sergeant of a secret military organization called Mithril, and he was ordered to protect Kaname from the terrorists. But why would anyone want to kidnap a simple high school girl? Find out in the anime :)