Yo-Jin-Bo: The Bodyguards

Sayori is a modern high school student with an interest in history. While helping her history club excavate the site of an old castle, she finds a jade pendant in the mud and takes it home. That night the pendant begins glowing and reaches out to the ghost of Princess Hatsuhime — a former resident of the very castle they were digging up. The connection that follows pulls Sayori far outside her ordinary life.