She's a highly energetic high school Street Fighter created by Capcom. Has learned most of her martial arts by imitating Ryu.
Sakura debuted in Street Fighter Alpha 2 as the youngest character in the franchise, and went on to star in numerous other games, as well as the odd manga or anime.
She is a martial arts enthusiast and high-schooler who took up martial arts after seeing Ryu, the Street Fighter series main protagonist, in action. Since then she has sought to emulate his style and methods. While she may not have Ryu's orthodox training, she is a surprisingly effective fighter, due to her talen and drive. Sakura's personality is generally optimistic, energetic and cheerful, though she sometimes doesn't think things through.
Sakura's first anime/manga appearance came in the officially-licensed Street Fighter Alpha manga by Masahiko Nakahira. She only appears briefly, however the seeds of her motivation are planted here when she is saved by Ryu, which ignites her interest in Street Fighting. She then went on to star in her own spin-off by Nakahira, Sakura Ganbaru, a 1996 manga which had a substantial influence on the later Street Fighter games. Following on from where Street Fighter Alpha left off, Sakura goes about her everyday life while honing her skills and aiming for Ryu, who she admires but knows nothing about, not even his name.
Sakura Ganbaru establishes a connection between Sakura, as well as Dan & Blanka, and other smaller elements like a friendship between Sakura and Cammy, all of which are mentioned in succeeding Street Fighter games. By far the biggest contribution to the franchise that this manga made though, was the creation of Sakura's rich rival, Karin Kanzuki, who actually became a playable character in Street Fighter Alpha 3.
Sakura also appears in the Street Fighter Alpha anime, where she has her first encounter with Ryu, and spends most of the movie pursuing him, but ultimately has little interaction with him.