[1] The series follows the story of Mochizuki Kotaro, a mild-mannered, unmanly high school student.
While visiting a library one day, he encounters Himiko, a mysterious librarian who recommends to him an ancient book about a heroic general from the Sengoku period, which occurred 400 years ago.
Kotaro notices that he has the same name and age as the general described in the book and experiences a flashback.
Kotaro later mentions the book to his father, who tells him that he may be the descendant of a powerful samurai.
At that moment, Kotaro receives a message from his childhood friend Ai, telling him that their classmate Nakamura Tsuyoshi is in trouble.