Sieg is an Imagin who enables Den-O's transformation into Wing Form. He arrives in the current timeline six months prior to Ryotaro becoming Den-O, originally intending to forge a contract with a young wealthy pregnant woman named Shiori Takayama, but possesses her unborn son in the process. After the child is born and subsequently kidnapped, Sieg comes into being and seeks to reunite his "brother" with their "mother", crossing paths with Ryutaros and gaining access to the DenLiner. Due to his "privileged" upbringing and his already princely mannerisms, Sieg becomes easily infuriated when treated with disrespect. Because he is "born" in 2007, he also possesses extraordinary unique abilities. Aside from shrinking the TarÅ�s to 4 inches tall with the phrase "Kneel down to me!" (é ã�Œé«˜ã�„! Zu ga takai!),he also cannot be forcibly removed from Ryotaro's body as he does not need a contract to possess humans. When possessing Ryotaro, Sieg says "Descending, yet above it all…" (é™�臨ã€�満をæŒ�ã�—ã�¦… KÅ�rin, man o jishite…). He almost vanishes due to his contract holder being a newborn child and unable to form proper memories, but Ryotaro is able to discover that Sieg actually made a contract with the mother to ensure her then unborn son's safety, saving Sieg's life in the process. As his contract has been fulfilled, the DenLiner takes Sieg to the date of his Shiori's greatest memory and lives in the past freely. After his appearances in the television series, he appears in the films Kamen Rider Den-O: I'm Born! and Saraba Kamen Rider Den-O: Final Countdown allowing for the transformation into Wing Form, and again in Cho Kamen Rider Den-O & Decade Neo Generations: The Onigashima Warship, pestering Tsukasa's group until brought to the climatic battle to join the TarÅ�s in forming Super Climax Form. He also appeared in Cho-Den-O Trilogy Episode Blue: The Dispatched Imagin is Newtral. During his first time on the DenLiner, he demanded that the others call him "Prince" (プリンス Purinsu?) and asked for Hana to be his "Princess" (å§« Hime?), and was punched for each time he called her that. After his return, Sieg refers to the TarÅ�s as his "family" instead of his "friend" phrasing. In the Imagin Anime OVA, Sieg had an additional power "Super-Ultra Kneel down to me!" (スーパーウルトラé ã�Œé«˜ã�„! SÅ«pÄ�-Urutora Zu ga takai!?) that allows him to shrink everything in sight, even an entire planet. His name is given as "Zieg" in the series' photobook DETAIL OF HEROES: Masked Rider Den-O Exclusive Photograph Collection: IMAGINE (DETAIL OF HEROES ä»®é�¢ãƒ©ã‚¤ãƒ€ãƒ¼é›»çŽ‹ç‰¹å†™å†™çœŸé›† IMAGINE DETAIL OF HEROES Kamen RaidÄ� Den'Å� Tokusha ShashinshÅ«: Imajin?), however, other materials give his name as "Sieg," such as the earlier photobook Masked Rider Den-O Photobook: IMAGIN (ä»®é�¢ãƒ©ã‚¤ãƒ€ãƒ¼é›»çŽ‹ãƒ•ã‚©ãƒˆãƒ–ãƒƒã‚¯ IMAGIN Kamen RaidÄ� Den'Å� Fotobukku Imajin?). Sieg's physical form and name are based on swan and Prince Siegfried (ジークフリート王å� JÄ«kufurÄ«to ÅŒji?) from the story Swan Lake (白鳥ã�®æ¹– HakuchÅ� no Mizuumi?).
An immortal companion of Yuta. She was raised by a group of old women that kept her captive and incapacitated in a hut. They were really mermaids that sought to eat Mana once she reached her adolescence to regain their youth. She travels with Yuta since, and possesses a large sense of loyalty and feelings towards him, but due to her somewhat naive and spoiled nature, she doesn't seem to truly realize that her emotions towards him are possibly love or just simple affection.
Ryutaros (リュウタãƒã‚¹) is the fourth Imagin that gives Ryotaro his power, which allows for the transformation into Den-O Gun Form. His natural weapon as an Imagin is a shotgun named the Ryuvolver (リュウボルãƒ�ー). Though he is the last Imagin to appear, Ryutaros initially possessed Ryotaro the moment that Urataros did, and simply hid himself from the others. Ryutaros reveals himself in his form when he is attracted by Naomi's coffee inside the DenLiner. Ryutaros is most childish in personality with a love for drawing and animals. Ryutaros also appears to enjoy break dancing, to the point to that it is incorporated into his flashy fighting style. His personality is one of a fun-loving dancer/disc jockey and is the most dominant Den-O has. This recklessness also causes the most collateral damage, as he fires his gun aimlessly. When he possesses Ryotaro, he first asks "Is it okay if…?" (…ã�„ã�„?, …Ii?, usually "Is it okay if I beat you up?" or "Is it okay if I end it?") followed by "Your answer doesn't matter" (ç”ã�ˆã�¯è�žã�„ã�¦ã�ªã�„, Kotae wa kiitenai).He has the ability to control people simply by snapping his fingers. This tactic works with summoning the Machine DenBird as well. Originally, Ryutaros possesses Ryotaro after being promised the title of become the DenLiner's conductor by Kai, who also gives the Imagin a ticket, on the condition that he destroys Ryotaro. However, because he does not wish for Airi to cry, Ryutaros decides not to destroy Ryotaro. The only individual he will listen to is Airi, whom he affectionately calls "sis" (ã�Šå§‰ã�¡ã‚ƒã‚“, onee-chan, Ryotaro only calls her the more formal "sister" (姉ã�•ã‚“, nee-san)). Because he knows that Airi has loved Yuto Sakurai, and from faulty advice on love from Kintaros, he becomes jealous of Yuto and wishes to show that he is stronger than him. But when Kai takes matters in his own hands in killing him, combined with realizing how he and Airi can not to be together, Ryutaros matures a bit to cope with fading away while eventually mustering courage to fight in the final battle against Kai. He usually refers to Urataros, Kintaros, Sieg, Teddy respectively as "Turtle-chan" (カメã�¡ã‚ƒã‚“, Kame-chan), "Bear-chan" (クマã�¡ã‚ƒã‚“, Kuma-chan), "Bird-san" (トリã�•ã‚“, Tori-san), and "Blue Bear-chan" (é�’クマã�¡ã‚ƒã‚“, Aoikuma-chan). However, he excludes Momotaros as he is not based on an animal and Momotaros does not understand him like the others do. He is referred to by the others as "Ryuta" (リュウタ, RyÅ«ta?). After this initial arrival on the DenLiner, he is rarely seen without a pair of headphones over his head. One of the TarÅ�s, Ryutaros's basis is unclear as early promotional material stated his form to be based on the legend of Tatsu no KotarÅ� (Taro the Dragon Boy) while TV Asahi's website for Den-O states that his form is based on Ryotaro's mental image of dragons. One of the Imagin Anime shorts discusses Ryutaros's possible namesake.
Kintaros is the physically strongest of the Imagin that are linked to Ryotaro and speaks Kansai-ben. He originally possessed a man named Masaru Honj�, but joins Ryotaro when Den-O is unable to defeat the Rhino Imagin. He is mostly found sleeping on the DenLiner, but will possess Ryotaro whenever he hears someone say anything resembling "cry" (泣�る� nakeru de). As Den-O, he lives up to his namesake and fights with an axe as Axe Form, has primary control of the left arm in Climax Form, and his power is tapped in the DenKamen Sword's KinAx mode.