Tumulus Gal Coffy: The Battle of Okehazama

Coffy, Daniel, and Okehazama-sensei accidentally entered the Forbidden Room behind the school building of Tumulus High School. When they managed to get out, they realized they had slipped back in time! Why did Okehazama-sensei become a fallen soldier? The truth behind the famous Japanese historical event, the Battle of Okehazama, is revealed!