From MangaHelpers:
Suddenly finding himself in the Sengoku era, regular high school student Sagara Yoshiharu is about to be killed in the battlefield. He is saved by none other than the man who later becomes the infamous Toyotomi Hideyoshi but at a cost to his life. With history completely changed because of Yoshiharu's actions, he tries to make things right again but it seems that history is taking a different course than the one he learned in school. Oda Nobunaga is now a brilliant but young girl named Oda Nobuna. Yoshiharu starts working under her command to bring back history to its correct course and find his way back home to the present world.