Momotaros is the first Imagin that gives Ryotaro his power, which allows for the Sword Form transformation. He can ense when an Imagin is rampaging in the city, alerting Ryotaro immediately. His natural weapon as an Imagin is a sword named the Momotarosword. Momotaros blames Ryotaro for his Oni-like form, though it matches his personality--passionate, haughty, and humorous, serving as a foil to Ryotaro's own shy and fearful personality. In fact, Momotaros is more interested in fighting than carrying out the Imagin's goal. He is constantly beaten by Hana when he gets Ryotaro into trouble. Momotaros is also somewhat selfish, initially fighting alongside Ryotaro in order to ensure his own survival. Though he unknowingly places Ryotaro in unneeded danger to suit his fancy, Momotaros eventually learns to respect him and his desire to protect others. Though he demands respect, Momotaros is usually put in his place by Hana and her powerful punches. He also does not know how to swim, has a narcotic reaction to red peppers, and seems to be afraid of dogs. While he acts hostile and demeaning to the other Taros, he does care about them, proven by hiding his anguish while they are slowly disappearing due to the events of the Climax Scene. Momotaros is the base for Den-O's Climax Form, as he has control of the head and torso and can control the other sections that the other Taros usually have primary control of if need be.
Urataros is the second Imagin that gives Ryotaro his power, to change into Den-O Rod Form. The form given to him by Ryotaro is turtle-like in appearance, with his weapon being the Uratarod, a rod with hexagonal blades at each end. Urataros was well-aware of Ryotaro being a Singularity Point, making his contract to him on purpose though he says it is to evade the loneliness of being outside time, Hana later debunks this entirely. When he possesses Ryotaro, he usually states the words, "Hey, will you let me fish you?" He is also aware of the evil Imagin planning to destroy time, but simply doesn't want to commit it as in spite of his cool exterior, there's indication that he's somewhat of a coward and lies just for self preservation. Urataros is a casanova with a very convincing personality with the ability to convince almost anyone by speaking to them, with Ryotaro the only one who trusts him and lets him stay as he sees he has a good heart. Urataros puts Ryotaro in conflicting situations when he goes around wooing multiple women. Urataros does show genuine concern for Ryotaro's well being the best speaker of the Taros, possessing Ryotaro simply to get information out of someone, or to talk his way out of something. He is also useful in situations that require patience.
Kintaros is the third Imagin that gives Ryotaro his power, which allows for the Ax Form transformation. He has a Sumo wrestler-like personality. He also has a habit of deep sleeping, until the mere mentioning of any word that sounds remotely similar to the Japanese word for "to cry" often provokes Kintaros out of his slumber to possess Ryotaro in an instant. His natural weapon as an Imagin is a giant battle axe named the Kintaros Ax. He has a habit of popping his neck every time he begins and ends a battle, as well having "You wept" as a battlecry. Kintaros is a strong Imagin who constantly seeks opponents stronger than him. Unfortunately, he is sometimes unable to control his own strength resulting in accidentally destroying things, which he attempts to fix afterwards. He is also very selfless and had no intent to follow Kai's orders to alter time to begin with. At first, he is dependent on a retired karateka named Masaru Honjo, as he attempted to master karate so Masaru could achieve the "ultimate karate". Kintaros wants to teach Masaru the ultimate karate, in order to let him settle things with Kikuchi instead of disturbing the time-stream. Seeing the good side of Kintaros when he protects Masaru from the Rhino Imagin and being mortally wounded in doing so, Ryotaro allows Kintaros to enter a contract with him, saving the Imagin's life. Unlike the others, who had selfish intentions for assisting Ryotaro, Kintaros's motives for helping him are noble from the start, having a desire to repay Ryotaro for saving his life, stating so on several occasions.
Ryutaros 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. 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. He enjoys break dancing, to the point to that it is incorporated into his fighting style. His recklessness causes the most collateral damage, as he fires his gun aimlessly. 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 doesn't 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". 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. He is also the only one of the Taros that actually possesses a ticket of his own, while the others share Ryotaro's ticket. After this initial arrival on the DenLiner, he is rarely seen without a pair of headphones over his head.
Deneb is an Imagin fully contracted to Yuto Sakurai, gaining a physical form within normal spacetime due to Sakurai's wish for the Imagin to aid his past self as part of their contract. Rather than possessing him to travel into the past, Deneb willingly betrays Kai and possesses Sakurai in the middle of a fight after witnessing his desire to protect time as Zeronos. Deneb serves as Yuto's butler and fights alongside him while he is in Altair Form, able to shoot bullets or smoke pellets out of his fingertips. He also provides Zeronos the ability to transform into Vega form. He carries around a basket that contains hand-made candies that have wrappers that bear his face called "Deneb Candy". His personality is the polar opposite of Yuto's, with Deneb's noble demeanor usually resulting in embarrassing consequences done to Yuto, who comically beats him up for it. Although Yuto treats him with occasional disrespect; Deneb chooses to stand by his side out of friendship and loyalty, knowing Yuto to be a kind person. He also acts as a parental figure to Yuto, doing his best to make sure he lives healthy, including a need to serve shiitake to him, despite Yuto's deep hatred towards it. Due to the fact he has a physical form in normal space-time, Deneb often appears in disguises in order to avoid standing out. Upon transforming into Vega Form, Deneb often starts out with "Let me tell you this for starters...", followed by something honest. The first instance was "This face on my chest is only a decoration!" Deneb's physical form is based on the historical story of Benkei and the fictional Karasu-Tengu. He is also named after the star Deneb in the constellation Cygnus the Swan which is important in the legend of the Tanabata along with "Altair" and "Vega", the names of the two forms that Zeronos can initially access.
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 rich pregnant lady 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 was "born" in 2007, he also possesses extraordinary unique abilities. Aside from shrinking the Taros to 4 inches tall with the phrase "Kneel down to me!", he also can't be forcibly removed from Ryotaro's body as he doesn't need a contract to possess humans. When possessing Ryotaro, Sieg says "Descending, yet above it all" 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 mom 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. He later pesters Tsukasa's group until brought to the climatic battle to join the Taros in forming Super Climax Form. During his first time on the DenLiner, he demanded that the others call him "Prince" and asked for Hana to be his "Princess", and was punched for each time he called her that. After his return, Sieg refers to the Taros as his "family" instead of his "friend" phrasing. In the Imagin Anime OVA, Sieg had an additional power "Super-Ultra Kneel down to me!" that allows him to shrink everything in sight, even an entire planet. Sieg's physical form and name are based on swan and Prince Siegfried from the story Swan Lake.
Teddy is Kotaro Nogami's Imagin partner from the future, able to assume the form of the Macheteddy sword New Den-O uses as Strike Form. He is a polite and reserved character in general, humbling himself to his friends. Unlike the other Imagin, his form is based on the stories that Kotaro was told by the Owner of his grandfather Ryotaro Nogami's exploits with the Taros as Kamen Rider Den-O. As such, the name he is initially given is "Neotaros", as evident by the designs resembling the letters NEO on his body, until Kotaro renames him after experiencing his grandfather's true meek life. Like Sieg, Teddy is a special case as he can sense whenever his contract holder is in any immediate danger and neutralize it. It has been described that Teddy is the Sancho Panza to Kotaro's Don Quixote.

Teddy first appears with Kotaro during the events of Saraba Kamen Rider Den-O: Final Countdown, both serving to replace Ryotaro and the Taros as protectors of spacetime. When Shiro travels back in time to May 23, 1729, and the New DenLiner gang follows, Teddy is the one who learns of Shiro's plans to attack the small village nearby and is seriously wounded by Shiro's forces. He recovers in time to help in the final battle against Kamen Rider Yuuki. But during the events of Episode Blue: The Dispatched Imagin is Newtral, Teddy is forced to set up a new contract with the Owner as his original contract had expired in the events of Final Countdown and is renamed Aleksandrovic. Though he nearly destroys himself in the process by derailing from his contract to help Kotaro, Teddy becomes his partner again.

An evil version of Momotaros, Negataros and a select few Imagin are stray Imagin who evaded the fate of the other evil Imagin when Kai ceased to exist in the final episode. From there, he comes to possess a stolen Rider Pass, allowing him to assume an evil version of Den-O Sword Form called Nega Den-O. Recruiting members of the Fangire Race and mobsters to his aid, Negataros intends to restore the future where the Imagin came from. But Negataros has to deal with both the DenLiner Police led by Ryotaro Nogami, an inside man in the form of Yuto Sakurai, further worsened by the brief meddling of Wataru Kurenai.

In the end, Negataros' plan is foiled and his armor is destroyed by the Double Boistous Kick & Darkness Moon Break of Kiva & Den-O Climax Form before he finally meets his end in battle while using the Nega DenLiner against the DenLiner, the ZeroLiner and Castle Doran.

Eve is an artificial Doberman Pinscher Imagin created the Time Police and partnered to Reiji Kurosaki. Being an artificial Imagin, Eve has infinite knowledge and is able to counter any attack which he uses greatly even when he is not the one fighting. Like Kurosaki, Eve has little emotion, thinking only about duty and performing judgement. But when Kurosaki starts showing emotion, Eve deems humanity too illogical to exist and becomes G Den-O himself to execute everyone. He was then destroyed after Diend in Complete Form used the Gekijouban card along with Kamen Rider Den-O Climax Form along with the G Den-O system.