Rappi rangai manga

Rappi Rangai summary:

This story takes place during the civil war in Japan. There is a mysterious boy with a short horn on his forehead. His life turns upside down after he saves a wanted female ninja, who then tells him that she's his servant and he an emperor! Soon a few more girls appear in his life and the adventure begins. What will happen to him and what kind of weird and wonderful stories lie in front of the small group is for you to find out.