|This article is about a/an alternate reality/A.R. World (another rider's world) in Kamen Rider Decade.|
The World of Agito (アギトの世界 Agito no Sekai) is the alternate reality where a version of Kamen Rider Agito takes place. Similar to the World of Kuuga, the Riders and the police battle the Gurongi. However, a new evil surfaces onto the world, monsters that they refer to as the Unknown. The backdrop used to enter the World of Agito is the elaborate tapestry seen in the opening sequence of Agito that depicts the story of Agito and the Unknown. This story arc further expands on the war between the Unknown and the Gurongi, which is hinted in both their respective series and explained more outside them. Within this A.R. World, Tsukasa assumes the role of a mailman with Toko's letter on his person. Due to the similarities to the World of Kuuga, Tsukasa more or less possesses the same talents in this world, as well as knowledge of the Unknown and the Agito power. Daiki's treasure in this world is the G4 Chip, but it was eventually destroyed by Toko.
Upon arriving in the World of Agito, Yusuke was shocked that there were Grongi in the world which were being dealt with by Kamen Rider G3-X. He was further shocked when he saw an interview with Tohko Yashiro, who was physically identical to the Ai Yashiro that died back in the World of Kuuga. Arriving at the police station, Yusuke offered to be the new user of the G3-X suit, but lost the position to Kaito. While this occured, finding himself in a mailman outfit with a letter to Shoichi Ashikawa, Tsukasa and Natsumi found the man before they were attacked by what they thought to be a Grongi. But during the fight, Tsukasa realized he was fighting an Unknown, an Ant Lord called Formica Pedes. After destroying the Ant Lord, Shouichi refused the letter before he and Tsukasa dodged an attack meant for him by a mysterious Unknown. Later that night, as Tsukasa read the letter's contents, Yusuke left the Hikari Studio to remain in the World of Agito with Toko. The next day, Kaito was deployed as G3-X to take out the Gurongi with Yusuke supporting him. During the fight, Kaito took off the armor to finish the Gurongi off as Diend, revealing that he only became G3-X for his own agenda. Though he destroyed Me-Ginoga-De, Zu-Mebio-Da attempted to run off only to destroyed by a couple of Formica Pedes. While this occurred, Tsukasa found Shouichi and offered protection, only to see him transform into Exceed Gills. Tsukasa attempts to restrain him as Kiva in Garulu Form. Gills, in pain of sensing the Ant Lords' attack, ran off and destroyed them both before Yusuke's eyes. When Diend targeted Gills, Decade tried to protect him, only to have his belt stolen by Gills with no defense against Diend's summoned Delta's Lucifer's Hammer finisher.
After Yusuke saved Tsukasa from Delta's attack, Gills was about to fight when he was overcome with pain as the Unknown shown up to kill him. As Shouichi escaped, Toko recognized him via G3-X's camera. While Tsukasa insisted on protecting an annoyed Shouichi, Yusuke reported the defeat of the Grongi and the emergence of the Unknown. He found Toko saddened, but had little time to help her as Kaito took the G4 chip stored within his locker. Yusuke demanded the chip back, but during the struggle, Toko blasted the chip to bits and a disappointed Kaito left. The next day, as Tsukasa continued to keep Shouichi safe from the Unknowns' attack, Yusuke learned that Shouichi was the original user of the G3 suit when he received the letter for Shouichi from Toko. As Gills fought the Buffalo Lord Taurus Ballista, Yusuke arrived in the G3-X suit to make Shouichi realize that Toko knew the truth and it was the reason for creating the G3-X suit. Diend arrived to selfishly aid them with Blade's power until Ballista arrived. But Tsukasa shown up to state the Buffalo Lord's ideological flaws as Shouichi awakened as Agito. As Diend took his leave, Decade, Agito, and G3-X battled Ballista and Formica Regia before the latter was destroyed by Agito. After turning Agito into the Agito Tornador, Decade and G3-X rode on the hoverboard to finish the Lord off. Soon after, Yusuke gave Toko his thanks as he said goodbye to her, and Shouichi returned to resume his place by Toko's side as Agito.
While his world vanishes along with the others, Shouichi is revived after Decade's death and helps revive Decade. He later appears to help in the final battle with Super Shocker, transforming into Shining Form as a result of Decade's K-Touch and later into his Agito Tornador form with the All Rider Final Form Ride Card to fight the Super Crisis Fortress.
- Shoichi Ashikawa
- Tohko Yashiro
- Taurus Ballista
In the novel reimagination of the Kamen Rider Decade TV series, Kamen Rider Decade: The World of Tsukasa Kadoya ~The Garden Inside the Lens~, the World of Agito is, as one of the Nine Worlds, not an alternate reality like in the TV series but the original world. The World of Agito is one of the six worlds the Hikari Studio group, Tsukasa/Decade, Kaito/Diend, and Natsumi, have already traveled to by the start of the novel as they head for the three remaining worlds, and thus not much is seen about it.