Short answers, pulled from the story.
Capcom released Street Fighter with a character named Ryu at its center in 1987. Game designer Takashi Nishiyama chose to create a karate practitioner wearing a traditional white gi after discarding an initial concept of a Caucasian man in a leather jacket.
Capcom released Street Fighter with a character named Ryu at its center in 1987. The original red bandana appeared due to an oversight but remained because it looked cooler than long hair.
Capcom officially labels Ryu's fighting style Ansatsuken Karate, though they acknowledge influences from Kyokushin, Shotokan, Kempo, Taekwondo, and Judo. His three special techniques include the Hadoken energy attack based on the wave motion gun from Space Battleship Yamato.
Ryu has appeared in numerous non-Street Fighter video games since his debut including Marvel vs. Capcom, SNK vs. Capcom, Namco × Capcom, Tatsunoko vs. Capcom, Project X Zone, and Project X Zone 2. He joined Super Smash Bros. for Nintendo 3DS and Wii U where he was recreated with new moves because the controller offered more buttons.
Live-action adaptations began with the 1994 film where Byron Mann played Ryu as a supporting protagonist. Director Steven E. de Souza wanted Mann but Capcom preferred Kenya Sawada who spoke English poorly so they used Mann instead.