The manga follows the story of 16-year-old Mana on an adventure through the Aquarian Age.
A sixteen year old girl, Mana returns to her hometown to reunite with her childhood friend after having been gone for seven years. But her friend, Kaname, seems to have changed too while they've been apart.
Mana's re-emergence soon sets off a series of events that alters the lives of Kaname and his best friend, Naoya. Classmates Isshin and Tsukasa, as well as their teacher Tomonori, find themselves drawn in as well.
Soon, they all discover that they have a part to play in the "Aquarian Age" - a war that has been secretly raging for thousands of years.
Now the future of the world depends on one girl and her destiny.
