15-year-old Goro Inagaki has just graduated from middle school. Blowing his last chance to confess to the girl he loves, Shiina Fujitani, he gets depressed and contemplates suicide. But just as he comes to his senses and decides life is worth living, his slips, hits his head, and dies anyway. However, it turns out his number wasn't meant to be up. Due to a clerical error in heaven, Goro died instead of another man with the same name. But when the angels try to fix this, another mistake lands Goro in the wrong body: a beautiful young girl the same age as him, a well-to-do millionaire's daughter, Hitomi Kusanagi, who also just so happens to go to the same high school as Shiina. What's more, Hitomi wants her own body back, and won't let Goro ruin her chances or her reputation.

In 1962, Isao Shibata debuted as a pitcher for the Giants, but his talent was overlooked and he was told to switch to the field. A young girl named Kiriko appeared in front of the discouraged Shibata and presented him with a secret book of Kouga Ninjutsu that she found by chance in her hometown. With her encouragement, Shibata vowed to make a fresh start as a fielder, and learned the secrets of the ninja arts written in the book one by one.

The year is 1961. Sadaharu Oh of the Yomiuri Giants, in a critical situation due to an injury during a game, had a sudden flash of insight that enabled him to read the thoughts of the opposing pitcher. He remembered he had a similar experience in junior high school. He tried various methods, but the ability of the future sight worked only once in five. After much anguish, he consulted with Coach Arakawa, who taught him to trigger his ability by putting himself in an unstable state with the one-legged hitting method. From then on, Ou mass-produced home runs using the one-legged batting technique to become the undisputed No. 3 hitter of the Giants and win multiple home run crowns.