Hideki Ryuga (流河 旱樹, Ryūga Hideki) is a Japanese pop-star and actor who stars in his own television show.
Ryuga has messy, yellow-green hair that reaches his neck, and his bangs hang down over his eyes. He is considered to be an attractive man by many women.
Initially, Ryuga is only seen on TV in a show that Sayu Yagami watches. Sayu seems to be a big fan of Ryuga, as she complains to Light when he suggests she change the channel while Ryuga's show is on. Later, when L decides to reveal himself to Light at the To-Oh University entrance ceremony, he uses Ryuga's name as an alias.
L's reason for using Ryuga's name is revealed by Light to not be just an alias, but also a trap, because if Light were to risk writing the alias into the Death Note to test the name, he'll most likely subconsciously picture the real Ryuga's face and end up killing the star instead, which would reveal Light's identity as Kira.
Ryuga himself eventually has an actual, albeit brief, appearance in the main story when Misa Amane lands a role as his love interest in a movie. While filming a scene where Ryuga is supposed to kiss her, Misa protests, refusing to kiss him due to her uncompromising faithfulness to Light, much to the frustration of the director.
His last appearance is at Pop Music Festival, where he is presented by Kiyomi Takada. He appears with other members of the cast of his upcoming show, "Ryouma Sakamoto" (in which he will be playing the title character, Ryouma), along with Ami Hamazaki, who would be playing his love interest.