Neo-Venezia has reached a long winter. Ai, Azusa and Anya, who were practicing jointly in the cold weather, visit the Undine Museum, led by Akira who seems not her usual self. At the museum, the trio meet its director, Asuka who is Akira's senior known as Himeya's legendary undine. The two of them are the successors to a gondola that has been carefully passed down since the founding of Himeya Company. However, Akira reveals that Aika, who is expected to inherit the gondola, has no intention of doing so. Azusa, who is not convinced, tries to find out why.

After Char's rebellion, Hathaway Noa leads an insurgency against Earth Federation, but meeting an enemy officer and a mysterious woman alters his fate.

Students, including Aoi Nishino, take part in class and sports activity at a prestigious high school. Aoi Nishino is a member of the school's archery club. He practices archery studiously and doesn't socialize much with the other students. His childhood friend Haruka Seno is also a member of the archery club, but she worries about Aoi Nishino. One day, thunder strikes the school grounds. After that, the ordinary lives of the students changes drastically. Many samurai descend on the school grounds. It appears that the entire school has traveled back in time to the Sengoku period. Making things worse, they realize that they are in the time right before the Battle of Okehazama takes place.