It is about the time-traveling adventures of six modern-day Japanese high school students from the St. Francisco Academy to the 17th century, where they take part in the Shimabara Rebellion.

The manga begins with the Great Hanshin earthquake of 1995, which the protagonists (a group of friends from the St. Francisco Academy from Kobe) barely survive.

Years later, during a school field trip to Nagasaki, the teenagers are thrown back in time to the Japan of the early Edo period.

However, Shirō was a very feminine-looking young man and the recently arrived Natsuki physically resembles him a lot, so the villagers think she is actually him.

Before long, Natsuki becomes famous as some-sort of heaven-sent angel and people started calling her "Shirō", believing she was the saviour prophesied twenty-five years before; she commits herself to their cause in an attempt to avert the soon-to-come rebellion, and gathers her lost partners as well so they can help her.