Kagerou-Nostalgia: The Resurrection (2002)

Blurb:
For centuries, the lands have been plagued by conflict. The people suffered, and many lives were lost as two powerful clans waged their decades-long war. But the brutal murder of the eleventh princess of the Hikami clan signals the beginning of a new era. The souls of those who died centuries ago have returned, housed within in the bodies of a group of courageous young boys and girls. Already, this group of special young teens knows that they must band together to once again face their enemy, the bloodthirsty Shogun. But the Shogun is a master of the black arts, and the only way the teens can defeat him is to train and develop their own supernatural power...

Source: www.anisearch.com/manga/3452