Ryu Terui is a fictional character from the Japanese tokusatsu series Kamen Rider W. He is known for being the second half of the main protagonist, Shotaro Hidari, and together they form the superhero known as Kamen Rider W. Ryu is characterized by his strong sense of justice and determination to protect the city of Futo from various threats. In the series, Ryu transforms into Kamen Rider W using the Double Driver and a special device called a Gaia Memory. His abilities allow him to harness the powers of different Gaia Memories, giving him unique skills and forms. Ryu's journey involves battling villains and uncovering the mysteries surrounding the Gaia Memories.