Yuki Shien (紫苑優輝, Shien Yuuki) is a main character exclusive to the Death Note film series. As a devoted Kira supporter, he uses his computer hacking skills to track down the six Death Notes in both Death Note: New Generation and Death Note: Light Up the NEW World.
Shien's family was murdered when he was young, but Shien survived the attack. Following his family's death, he was raised in an orphanage. Kira killed his family's murderer, and Shien became devoted to Kira. After Kira disappeared, Shien searched for him and became a cyber-terrorist to help the world.
Death Note: New Generation
In 2016, in the second episode of Death Note: New Generation, Shien finds Karin Kanatomo's video where she is controlled by a Death Note. Karin's last words are an anagram for "Kira, I have it too," and Shien hacks her laptop. He remotely turns on the webcam while Ryuzaki is in Karin's room investigating her murder. J notices that the camera has been turned on, giving Ryuzaki enough warning to put his mask on so Shien is unable to see his face. Shien learns about Sakura Aoi, the owner of a Death Note who sent the message through Karin.
The third episode focuses on Shien's history and his decision to use the Death Note. One day, a Death Note drops into his room. Shien chooses two criminals who murdered a family and were freed ten years earlier: Kazutoshi Namaki and Taichi Kunugida. He looks into them, and he personally confronts Kunugida before killing him.
Death Note: Light Up the NEW World
In the film Death Note: Light Up the NEW World, Shien continues searching for the other Death Notes. He kills Sakura Aoi in the middle of her murder spree, but is unable to obtain her Death Note because the Task Force is already on the scene. He uses his Death Note to control Chief Justice Kenichi Mikuriya into handing over his Death Note to Shien and then giving a message to the Task Force. At some point, he also procures Alexey Ivanov and Roger Irving's Death Notes. He convinces Misa Amane to help him after giving her one of the Death Notes to restore her memory.
During a face-off with Ryuzaki and Tsukuru Mishima, they are attacked with orders to kill. Shien is fatally wounded, so he hands the Death Notes to Mishima, who he now knows is the real Neo Kira. Shien takes out as many of their attackers as he can before dying.