Garrett Megg

"Let me say this to start: I am fairly strong!"

- Yuto's pre-battle catchphrase.

Kamen Rider Zeronos (仮面ライダーゼロノス) is the Secondary Rider that appears in Kamen Rider Den-O.

Garrett Megg
Garrett Megg is a man who bears the same name as Airi's fiancé who mysteriously disappeared prior to the beginning of the series, but similarities do not go any further it would seem. It is later revealed that Yuto is the very same Yuto Sakurai, only a decade younger, sharing his future self's high knowledge of astronomy. Prior to the series, Yuto Sakurai encounters his future self, the older Yuto Sakurai of 2007, who revealed to him the situation relating to the Imagin. Provided with the Zeronos arsenal and Deneb, Yuto takes the ZeroLiner forward in time to May 20, 2007.

Unlike Ryotaro, Yuto claims that protecting the flow of time is not the same thing as protecting people. He says that saving people is unnecessary if it means disrupting the flow of time even if it means sacrifices must be made to save the future. He holds a very spoiled personality, and often acts like a child when things do not go his way and putting lots of sugar in his coffee before actually tasting it, hence earning him the nickname "Boku-chan" (僕ちゃん) by Urataros. Yuto is also the kind of figure who would use dishonest methods to get the job done, but has since abandoned this way of fighting. A running gag with Yuto is his hatred for shiitake mushrooms, going as far as a comic beating to make sure Deneb does not serve any.

After Yuto disappears in time (during the events of Cho Kamen Rider Den-O & Decade Neo Generations: The Onigashima Warship), an even younger version of Yuto appears known only as "Yu". Yu possesses an artifact that the Oni Brothers Goludora and Shilubara need to complete their plan. Thus Ryotaro, Kotaro and the rest of the Den-Liner crew aid him and get the artifact to the past. To protect Yu, Deneb, not knowing he is actually Yuto, asks to form a contract with him, allowing him to gain a physical form. Yu's wish for the contract is for Deneb to see his contract holder, once more. The adult Sakurai and the ZeroLiner make a cameo appearance in the end, with the former reuniting with Deneb. Yuto returns once more when his relationship with Airi begins to be threatened by the actions of the Piggies Imagin (the events of Episode Red: Zero no Star Twinkle).

When possessed by Deneb, Yuto's hair grows out past shoulder length with two locks of hair on each side of his head. On the right side, the lock is a neon green with a darker green streak within it. His personality is also overwritten by Deneb's, who is much more polite and apologizes for Yuto's actions, often by giving out Deneb Candies and acting overly friendly. This usually gets Yuto angry thus forcing Deneb out of him and comically beating him. In one occasion, he was also possessed by Urataros. Although surprised and initially annoyed, he allowed the possession to happen for a short while.

Fictional character biography
Prior to the series, Yuto Sakurai encounters his future self, the older Yuto Sakurai of 2007, who revealed to him the situation relating to the Imagin. Provided with the Zeronos arsenal and Deneb, Yuto takes the Zero-Liner forward in time to May 20, 2007, where he makes himself known to Ryotaro Nogami after the Wolf Imagin is destroyed. He warns Ryotaro not to look for the mysterious man in the trenchcoat, the future Yuto Sakurai that Ryotaro knows as his sister's fiancé. Yuto also reveals that he is Kamen Rider Zeronos, chiding Ryotaro's flawed ideals as Den-O yet was unhinged when Ryotaro intended to keep fighting for what he believes in. Once he meets his near-future self, who abducts Ryotaro to prepare for an event known as the Climax Scene, Yuto begins to respect the boy chosen to be Den-O.

Yuto originally has ten Zeronos Cards, the items that allow him to become Zeronos, which are in turn are tied to the memories people have of the elder Sakurai. Each time a card is used up from a battle, the memories from normal people who knew Sakurai disappear as well. It is this reason that he tries not to become Zeronos very often, only doing so if it is necessary to help Den-O. After using up his second-to-last card in an attempt to save Deneb, only to learn it was a false alarm, Yuto is reluctant to use his final card until Airi is kidnapped by Fujishiro, one of her former suitors that has been possessed by the twin Anthopper Imagin. He uses his last card as Airi begins to remember him, making Fujishiro and Airi lose all memories of the Sakurai they knew. Unable to become Zeronos, Yuto is confronted by Sakurai himself, receiving another set of Zeronos Cards despite Deneb's protests. These new cards show that the older Sakurai is displaced from time and space during each transformation, as memories of him alone cannot power the cards. As Kai arrives, Kai sees fit to eliminate Yuto Sakurai, as he believes that Sakurai is the key to the Junction Point. Kai sends the female Snail Imagin to 1993 to kill Yuto before he could meet Sakurai, removing him from time.

However, the Zeronos Cards have created a time lag, allowing Yuto to return despite not being a Singularity Point like Ryotaro. He also uses red Zeronos Cards, which Ryotaro notices. Yuto tells him that the memories of the older Sakurai are no longer enough to support Zeronos' power, and now his memories in 2007 are being used as power to transform him into Zeronos Zero Form. Eventually, Kai starts to question his agenda and realizes that Yuto and his future self have been acting as a distraction from his true target: Airi, who is tied to the Junction Point. Once Ryotaro goes into the past, Yuto is forced to battle the numerous Imagin under Kai, fighting them and the Death Imagin to protect Airi until Ryotaro returns.

When Ryotaro does return, Yuto fights alongside him using the last card Deneb gave him, which severs his ties to his future self. After the battle is over, Yuto immediately returns to the Zero-Liner to find Deneb only to find nothing but the last meal Deneb prepared for him, which ironically has shiitake in it. Yuto willingly eats the meal as Deneb surprises him. Instead of comically beating him up as normal, Yuto instead hugs Deneb, crying tears of joy. After Yuto, Hana, and Ryotaro discuss their respective futures, Yuto gives Hana a pocket watch, which signifies a possible meeting in the future. Yuto and Deneb say their goodbyes to Ryotaro as the Zero-Liner departs into the time stream.

Later, Ryotaro finds Yuto having been investigating the crime lord Seiya Kuroki undercover and discovering his ties to Negataros. Yuto and Deneb manage to maintain his guise of being a villain in the ranks until Ryotaro's partner Suzuki gets himself caught by the evil organization. Attempting to save Suzuki, he gets caught in Negataros' trap to draw out the detectives pursuing him. In the ensuing battle, Yuto is revealed to be in possession of more regular Zeronos cards.

Yuto and Deneb later return to aid the Den-Liner Crew when Ryotaro is abducted by Shiro, joining the epic battle against the revived Imagin and the villains of the Phantom Train.

After a time anomaly (attributed to Kamen Rider Decade) causes Yuto to disappear in time, an even younger version of Yuto appears in the film Cho Kamen Rider Den-O & Decade NEO Generations: The Onigashima Battleship, though the entire cast only know of him as "Yu". Yu-kun possesses an artifact that the antagonists wish to have. Thus Ryotaro, Kotaro and the rest of the Den-Liner crew aid him and get the artifact to the past. To protect Yu, Deneb, not knowing he was Yuto, asks to form a contract with him, allowing him to gain a physical form. Yu's wish for the contract is for Deneb to see his contract holder again. It is most likely that the Yuto from 2007 will return to Earth because as he is Hana's father and Hana still continues to exist, although having a younger body, so in the Den-O universe, he will definitely return from his displacement.

OOO, Den-O, All Riders: Let's Go Kamen Riders
Kamen Rider Zeronos was part of a group of reinforcement riders led by Akira Date/Kamen Rider Birth to aid the primary riders in defeating the Rock Great Leader. All the Kamen Riders got on their bikes and performed the All Rider Break attack which destroyed the Great Leader.

Kamen Rider Climax Heroes
Kamen Rider Zeronos appears in all Kamen Rider Climax Heroes series video game. In the first and Kamen Rider Climax Heroes Double, his Zero form only being used as special move and finishing move.

All Kamen Rider: Rider Generation 2
Kamen Rider Zeronos appears in All Kamen Rider: Rider Generation 2.

Kamen Rider Battride Wars
Kamen Rider Zeronos appears as a Second Rider in the video game Kamen Rider Battride Wars.

Forms
Unlike Kamen Rider Den-O, Zeronos uses a card system, using Zeronos Cards to activate the transformation process. A Zeronos Card disappears after use, which limits the number of times the Zeronos transformation can be achieved as each time a card disappears. At the beginning, Zeronos had multiple forms that he could assume in battle. On his own, Yuto could become Kamen Rider Zeronos Altair Form. When the Imagin Deneb possesses him, he is able to become Kamen Rider Zeronos Vega Form. Altair and Vega Form are based on the Summer Triangle, which is part of the myth that is the basis for both the Chinese legend of Qi Xi and the Japanese Tanabata Festival. A cowherd named Niu Lang/Hikoboshi (Altair) is separated from his lover and the mother of his children, the fairy Zhi Nü/Orihime (Vega), by the great river (the Milky Way) as punishment for the fairy having eloped with a mortal man. Every year, the magpies take pity on the two lovers and become a bridge at Deneb to allow the two lovers to be together once again.

Kamen Rider Zeronos' ending theme is entitled "Action-ZERO".

Altair
Altair Form "Altair Form!"

- Transformation announcement

Altair Form (アルタイルフォーム) is the default form of Zeronos, using the Zeronos Cards to evoke the change. It is named after the star Altair in the constellation Aquila the Eagle. The "mask" is made up of two green bull's head-shaped visors, the same motif as Zero-Liner Drill, which is based on the mythological occupation of Altair as a cowherd. These form from two bull's head-shaped train cars that ride along the tracks on Zeronos' helmet. The rest of the body has a set of converging train tracks that are almost like a zipper. Altair Form has generally balanced abilities comparable to Den-O's Sword Form. When Yuto becomes Altair Form, he says, "I'll tell you this for starters…" (最初に言っておく…) followed by something that concerns Yuto's strength or how annoyed he is. After using the Red Zeronos card, Yuto's own memories were used to cause Altair Form to "rust", changing it into Zero Form, although the future Yuto Sakurai is still able to assume Altair Form. In the final fight, Yuto once again uses this form using the last of the original Zeronos cards. Later during the investigation of Negataros, Yuto returns with a new set of Zeronos cards, able to assume Altair Form once again.
 * Rider height: 192cm
 * Rider weight: 89kg
 * Ability perimeters:
 * Punching power: 5t
 * Kicking power: 7t
 * Maximum jump height: 35m
 * Maximum running speed: 100m/5s

Vega
Vega Form "Vega Form!"

- Transformation announcement

Vega Form (ベガフォーム) is the form of Zeronos that comes from being possessed by the Imagin Deneb. It is named after the star Vega in the constellation Lyra the Lyre. It has a series of cannons on its shoulders called the Zeronos Nova (ゼロノスノヴァ). In the process of transforming into Vega Form, Deneb's body makes up various aspects of the form: his face is on Vega Form's chest, his hands form the Zeronos Nova, and his cloak becomes the cape. The "mask" is made up of a spool of thread, as Vega is a weaver, that opens up into a star shape. Vega Form is physically stronger than Altair Form, although suffers a loss of speed and overall agility. Whenever Deneb possesses Yuto to assume Vega Form, he says "I'll tell you this for starters…" (最初に言っておく…), following with a honest fact that annoys both the opponent and Yuto. Vega Form is accessed for the last time during the final battle, playing a part in the destruction of the Death Imagin, although Yuto assumes the form once more in the fight against Negataros.
 * Imagin: Deneb
 * Rider height: 199cm
 * Rider weight: 123kg
 * Ability perimeters:
 * Punching power: 7t
 * Kicking power: 10t
 * Maximum jump height: 25m
 * Maximum running speed: 100m/9.7s

Zero
Zero Form "Charge and Up!"

- Transformation announcement

Zero Form (ゼロフォーム) is a form of Zeronos that Yuto can assume, visually similar to Altair Form, but with a red color scheme (in place of Altair Form's green parts) and golden trimmings. After Yuto used the first Red Zeronos card, it used his own memories as a catalyst to cause the green portions of Altair Form to rust dramatically, turning them red and giving the armor a rustic-like texture while increasing its capabilities. As he did with Altair Form, Yuto can now assume Zero Form on his own, with access to the Denebick Buster. Zero Form is lost when Yuto is defeated by the Death Imagin using his last Red Zeronos card, but is later regained through unknown means in time to aid the Den-Liner crew against Shiro and the revived Imagin. Possibly because memories of him are being made in the present time. Unlike his other two cards, when the Zero Form card is inserted into the belt, it will exclaim "Charge and Up".
 * Rider height: 192cm
 * Rider weight: 89kg
 * Ability perimeters
 * Punching power: 7t
 * Kicking power: 9t
 * Maximum jump height: 42m
 * Maximum running speed: 100m/4s

Device

 * Zeronos Belt: Transformation Belt
 * Zeronos Card: Cards that allow Zeronos to change forms and perform attacks

Weapons

 * ZeroGasher: Personal weapon
 * Zeronos Nova: Personal weapon in Vega Form
 * Denebick Buster: Zero Form's primary weapon

Vehicles

 * Zero-Liner: Zeronos' personal train
 * Machine ZeroHorn: Zeronos' Rider Machine