Hana is a Singularity Point and the first DenLiner passenger Ryotaro met, convincing him to become a Kamen Rider while explaining the uses of the Rider Tickets and the Rider Pass. She said that she fights so that she can protect and preserve the flow of time from the Imagin, and she made a contract with the DenLiner's Owner to do so. She comes from a future destroyed by Imagin chaos, still existing because of her status as a Singularity Point. With no timeline to call her home, Hana is filled with malice and spite towards the Imagin, making her capable of subduing the Taros when they get out of line. Hana did grew closer to the Taros over the course of the series, briefly crying when Urataros, Kintaros, and Ryutaros disappear, though she refuses to admit it. Hana usually worries and looks after Ryotaro, treating him like a younger brother.
Over time, the tracks that represent Hana's future were being recreated, resulting with Hana turning into a child. Despite being in the body of a ten-year-old, under the alias of Kohana, she is still able to subdue the Taros when they get out of line aboard the DenLiner. In the finale, she is revealed as the daughter of Airi and Sakurai (thus being the niece of Ryotaro), the true key to the Junction Point and Kai's downfall as her future connects to the present. However, as her place in time is yet to be restored, Kohana lives on the DenLiner to await for her time. She becomes a member of the DenLiner Police at one time, aiding Kazuya Suzuki by taking out Kuroki's men single-handed.
Naomi is the waitress of the Den Liner's dining car, the setting of nearly all of the action aboard the Den Liner. Despite her efforts, she usually serves poorly made coffee, though the Imagin cannot resist it. She is extremely hyper and does not get surprised easily, sticking to her belief of making only coffee. She is good friends with the Taros Imagin and is usually seen playing with Ryutaros. During the series finale, Naomi takes the Den Liner back from the New Mole Imagin and uses it to go into the past to retrieve Urataros, Kintaros, and Sieg for the final battle with Kai's army of Imagin.
The Owner of the DenLiner is Hana's contractor, with a habit of speaking in complex riddles when it comes to the nature of time. He states that only those with a "Pass" are able to ride the DenLiner and, with it, transcend time itself. Also, as the DenLiner's owner, he can't stand fighting in his train and any who dare alter the flow of time. Owner possesses Passage Denial tickets, which are able to leave unwanted passengers stranded in the middle of time unless they have tickets. He has great knowledge of how time progresses and points out that sometimes the most minor of changes will not affect the future. He also happens to be a Singularity Point as he displays immunity against Ryutaros's ability to control people, even returning a similar tactic against Ryutaros himself. He is able to outrun the DenLiner and held a Master Pass until Gaoh took it from him. In Climax Deka, Owner is robbed of the spare Den-O Pass he owns during his training, setting up the DenLiner Police with himself as Chief Inspector. He carries a spare DenGasher that he uses to calm people down by shooting his trademark flags as tranquilizers.
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.
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.
Airi Nogami
Airi Nogami is Ryotaro's elder sister and owner of the Milk Dipper that belonged to their parents. Most of her customers are young men who all have a crush on Airi, often leaving her a multitude of gifts that, Airi leaves in the lost and found for the cafe. A motherly figure to her brother, she constantly tries to help Ryotaro in an attempt to find his lucky star. Originally, she was to be married to Yuto Sakurai on January 10, 2007, pregnant with their unborn child who is the Junction Point. However, Kai's intent to kill them to destroy the Junction Point forced Airi to allow Sakurai to erase himself and their child from normal time so they can evade Kai and his Imagin army. This resulted with Airi losing all memory of her fiance Sakurai. Although she actually goes to the place she and Sakurai spent time together, the park at Kibogahara after being hypnotized by Miura on accident, she can't remember much, particularly about the railway watch which is all that Sakurai left. When she encounters Fujishiro and is kidnapped, Airi begins to clearly remember Sakurai until Yuto uses his final Zeronos Card, wiping her memories of his future self as a result. When Yuto later uses the red sided Zeronos Card, all of his memories with Airi are burned away when he assumes Zero Form for the first time. But eventually, when Ryotaro meets Airi's past self, she is revealed to have known about Sakurai obtaining the ZeroLiner and the identity of the Junction Point: their daughter Hana. In the series finale, Airi regains her memories of Sakurai as they meet one final time before he fades from existence, though she is confident that they will meet again in the near future.
Seigi Ozaki
Seigi Ozaki is the journalist who is the chief editor of a short-lived magazine where Ryotaro worked. He is always looking for a new good story to restore his magazine, sometimes revealing Imagin attacks to Ryotaro this way. He is a regular customer at the Milk Dipper and is trying to court Airi. Ozaki also has a habit of flirting with other women since first grade, despite the fact that he focuses on Airi. During Climax Deka, Ozaki learns the truth behind Ryotaro when Airi takes him and Miura into the DenLiner.
Isse Miura
He is self-styled counselor and a regular customer at Milk Dipper and is also trying to court Airi, but he is more introverted than Seigi in this regard. He believes that Ryotaro is possessed by evil spirits after witnessing the "confrontation" between Momotaros and Urataros. Unknowingly, his attempt to hypnotize Ryotaro in hopes of exorcising the evil spirits result in Ryutaros revealing himself. As a result, Miura is the only one who is somewhat aware of the Taros' possessions, though no one believes him until Climax Deka, where Airi brings him to the DenLiner to see Ryotaro.
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.
Past Man
The "Past Man" is a mysterious figure that appears in times in the past when Imagin, who are out to get him. He has a Seiko pocket watch that has the phrase "The past should give us hope" on the back etched on it. When Ryotaro bumps into the "Past Man" at one point, he saw that he was the Yuto Sakurai he knew: Airi's fiance who mysteriously disappeared and is believed to be dead. Ryotaro remembers him as a kind figure who was into astronomy and loved Airi's coffee, and as such, almost considered him family. As he is Yuto's future self, Sakurai has access to the Zeronos arsenal. Eventually, the memory of Sakurai is completely erased from mostly everyone within Ryotaro's time. This happens because Sakurai provided Deneb with the first set of Zeronos Cards Yuto uses at the cost of his future self's existence, with the final Zeronos card presented to Yuto in the final battle completely erasing him from time. Though Airi is confident that her love will return to her in time.
Station Master
The Owner's rival, they compete with eating their meals complete without the flag that is placed in, falling out. Though the two look identical, with the Station Master wearing in white uniform and having effeminate mannerisms, Owner explains that the resemblance is just everyone else's imagination. Knowing that it would be last time before facing him again with the final battle against Kai about to begin, Owner finally beats the Station Master with the flag barely falling over.
Series:  Kamen Rider Den-O