Suddenly finding himself in the Sengoku era, regular high school student Yoshiharu Sagara is about to be killed in the battlefield. He is saved by none other than the man who later becomes the respected Hideyoshi Toyotomi but at a cost to the latter's life. With history completely changed because of Yoshiharu's actions, he tries to make things right again. However, history takes a different course than the one he learned. Yoshiharu meets a brilliant but young girl named Nobuna Oda. Yoshiharu starts working under her command, who nicknames him Saru (monkey), to bring back history to its correct course and find his way back home to the present world.