Idol Ace

Satomi Azusa is a popular teenage gravure idol. She's also a highly talented baseball player, but, as a girl, she can't play on her school's team. Her father happens to be the coach of the team, and he concocts a scheme to allow her to play. His scheme involves Hirayama Keita, Azusa's childhood friend, a teenager of no particular talent. Keita's redeeming feature is that he looks a lot like Azusa. In fact, after putting Keita in a wig and girl's clothes, not even their parents can tell the two of them apart. To help Azusa's (and her father's) dream come true, Keita agrees to trade places with her during the baseball games. Soon "Hirayama Keita" becomes a popular player, and "he" begins to move towards a career in pro baseball. How long can Keita and Azusa keep up the act? What will happen when people find out?

(Source: MangaHelpers)

Note: The first 3 chapters were collected in Short Program 3.