Sidoh is the Shinigami whose Death Note was stolen by Ryuk. By the time he realizes this, however, the note has already changed hands several times, ending up in the hands of Mello's gang (more specifically, Mello's subordinate, Jack Neylon). After repeatedly hounding Ryuk for its return, he tracks down the gang to get it back. In order to regain his Note, Sidoh agrees to help Mello's gang against Near's SPK and the Kira investigation team. He wears heavy clothing, obscuring most of his features, and his head is wrapped in bandages. He is voiced by Kazuki Yao in the Japanese anime and Sam Vincent in the English dub.
Sidoh shares Mello's great liking for chocolate, similar to Ryuk's liking of apples. Sidoh is fairly timid; Mello frightens Sidoh, despite the fact that Mello is a human. Death Note 13: How to Read describes Sidoh as unintelligent and forgetful, rarely remembering the names of other Shinigami. After Light regains the Death Note from Mello, he returns it to Sidoh to keep him from interfering.
Obata described Sidoh as "very funny," citing the time when Sidoh becomes the first Shinigami to distribute flyers. Obata said he wished that Sidoh appeared more often in the story.