KaguRai: Kagura & Raito

Kagura is a female swordsman who was born to a distinguished family, and followed the path of the blade. Kagura has a friend name Raito who is a "human apparition". Ten years ago, Kagura was told that Raito will eventually be considered a full-fledged ghost, and so she made a promise to travel the world with the "human apparition" before they were separated. And now, she begins to take action in order to fulfill that promise!! Source: Shogakukan