From "Kamen Rider Double"

Nasca Dopant:http://i231.photobucket.com/albums/ee121/Kainsword17/Dopants/04NascaDopant.jpg

Kirihiko Sonozaki is a young man who works for Ryubee, one of his best Gaia Memory dealers with a love for the city of Futo. Before being hired by the Sonozaki family and courting Saeko, he was a press agent, and in his youth he created the city's mascot Futo-kun. He marries Saeko, being noted as the only man she allowed to live after a date, changing his surname from Sudo. As Ryubee's way of accepting him into the family, Kirihiko receives a Gaia Driver and the Nasca Memory, allowing him to assume the form of the Nasca Dopant. As the Nasca Dopant, he wields a sword as his weapon along with his ribbons along with generating wings of energy and balls of plasma. When he reaches Level Two of his Gaia Memory's ability, he can move at blinding speeds. However, this carried an unintended side-effect as it slowly kills him.

Because he is an in-law, not being well trusted by Ryubee, Kirihiko does not know the full truth behind the Gaia Memories and is initially unaware of Double's existence until encountering the Kamen Rider personally and then fighting him face-to-face in a battle that ends in a stalemate. When first encountering Shotaro, he believes that the man is one of Wakana's stalkers. However, he eventually discovers that Shotaro is the Kamen Rider, seeing him as a rival keeping him from his goals and putting him of out good graces with Saeko until he secretly gains his Level Two abilities and uses them to save her from harm. However, after he discovers Museum's existence and how evil it truly was as he was used to test the full abilities of the Nasca Memory, Kirihiko could no longer support the Sonozaki Family. When he expresses this to Saeko, attempting to get her to leave with him, Kirihiko is killed by her as she takes the Nasca Memory and leaves.

©Toei