粉丝盖亚、奥菲诺克、魔化魍……。到现在为止的所有怪物突然出现，开始袭击人类。救了被袭击的光夏海的，是变成decade的门矢士。然后，红渡出现了，告诉了这次事件的关键。

空我的世界。 在这里，空我-小野寺佑介在侦探八代爱的支持下与格隆基作战。 门矢士决定这个世界警察的身份一起行动，并挑战与格隆基。

空我的世界。虽然decade阻止了格隆基的gegal，但是不可能觉醒的“究极的黑暗”-·加米奥·泽达复活了。在这个空我的世界，毁灭的现象开始出现了……

牙的世界。Fangire和人类在这里和谐相处。门矢士遇到了一个拉小提琴的少年——渡。当渡知道门矢士是decade后，变身成牙，向decade发起攻击。双方展开了激烈的战斗……。

龙骑的世界。为了调查这个世界的骑士，光夏海访问了《Atashi杂志》，但讽刺的是，光夏海因涉嫌杀害主编玲子而被捕。然后，夏海不知为何要受到假面骑士审判制度的审判…。

龙骑的世界。真治怀疑杀害主编玲子的真凶是莲。但是，雄助说他愿意相信莲。与此同时，莲在镜子世界里发现了奥丁的身影，独自一人挑战了骑士战争…。

剑的世界。在这个世界里，假面骑士隶属于一个叫“BOARD”的企业，拿着工资和不死人战斗。假面骑士剑= kazma是最高等级的王牌职员，但是因为打破公司规则救了人命…。

剑的世界。卡祖马被突然出现的传说中的假面骑士卡里斯夺走了布雷卡扣。门矢士成为了一马的上司，开始对员工食堂进行改革，在夏海和雄助的协助下成功扭亏为盈。另一方面，kazma也意识到同伴的重要性…。

Faiz的世界。这个世界的门矢士，是smartbrain高中的学生。为了保护同为摄影部的由里不受奥菲以诺的攻击而变身成Faiz，但是受到奥菲以诺的攻击，变身被解除了…。

Faiz的世界。百濑等幸运四叶草，显露出奥菲以诺的本性，开始袭击由里和学校的学生们。失去变身Faiz腰带的塔克美，为了保护她们，在学生们恐惧的眼神中变成了wolforphenok…。

亚极陀的世界。在这个世界，未确认生命体和警察的战斗也在持续。雄助发现了与在空我的世界中死去的八代刑警有着相同的身姿和名字的女性，为了帮助她而成为了G3-X的候补驾驶员…。

亚极陀的世界。翔一在艾克西多吉尔斯觉醒后，被安乃运盯上了。对于警告不要接近自己的翔一，门矢士顽固地策划保护翔一不受厄运的袭击…。

电王的世界。 几天来，Imagines 一直处于无法保持实体的状况。 浦太郎等人认为原因在于Decade，附身光夏海的身体，变身为Den-O，反复改变形态攻击Decade。

After getting on the DenLiner, Tsukasa takes pictures of the DenLiner's gang before the Taros. But after Kohana sets the three Imagin in their place, they suddenty find the Hikari Studio as the front car. Kohana explains to Natsumi about the Imagin's new attack pattern as well as Momotaros, who Tsukasa decides to find. After surviving his confrontation with Diend and taking out another Mole Imagin, M-Yusuke tends to his injuries as Tsukasa finds him and scolds him for being an idiot. M-Yusuke senses the Imagin boss, and he and Tsukasa chase after the Alligator Imagin until he reveals himself. Using the Mole Imagin to cover his escape into the past, the Alligator Imagin battles Den-O and Decade, using the former's own DenGasher against him.

After helping the DenLiner gang in the past, Tsukasa and company begin their venture in the World of Kabuto. Posing as a ZECT Trooper, Tsukasa is deployed to aid Bright Troopers in the containment of a Worm as Kamen Riders Gatack and TheBee manage to exterminate it with the unseen aid of Kabuto. Soon after, Tsukasa brings Arata to the Studio to explain about his world, only to find a Worm had mimicked Tsukasa's form. After Natsumi uses the pressure point to expose one of the Tsukasas as a Worm, Decade fights it before it attacks a girl and is destroyed by Kabuto. Deciding to investigate the girl Mayu, they host a photo shoot for her, and Natsumi learns of Mayu's older brother who was supposedly killed by Kabuto. At ZECT's headquarters, TheBee's user, Sou Otogiri, tells Arata that the final prepation for the plans to capture Kabuto are nearly done.

Believing that TheBee's user is her brother, Mayu attempts to look for him with Natsumi's aid until they are attacked by a Worm. Counting on Kabuto to save them, Diend fights him to acquire his Clock Up system, summoning Ixa and Psyga to hold him down before Kabuto defeats them and runs off. By the time Tsukasa finds Natsumi and Mayu, the latter is shocked that she became a Worm as she runs off. She runs into Sou who reveals himself as the Phylloxera Worm and brings her to ZECT HQ as part of the Kabuto Capture plan, much to Arata's dismay before he is beaten to a bloody pulp questioning the plan. After escaping, Arata makes his way to Tsukasa and reveals the plan to him, confirming Tsukasa's notion. Kabuto falls for the trap as the Clock Down takes effect while the Worms reveal themselves among the ZECTroopers, with Sou exposing Kabuto as Mayu's real brother Souji.

Arriving in the last world, the World of Hibiki, Tsukasa and company begin the search for Kamen Rider Hibiki when they are ambushed by the Makamou Kappa. An Oni in training named Asumu battles the monster until Decade uses Kabuto's powers to destroy it. On learning he is Hibiki's pupil, Tsukasa has Asumu bring him to his mentor. Upon seeing Tsukasa, Hibiki, who is shirking off from his duties as an Oni, believes him to be the legendary Ongekidō Grand Master. Meanwhile, Zanki slays a band of Bakeneko as Ibuki arrives to take them out as well. But when the last Bakeneko escapes them, Decade destroys it with the two groups as witness. Tsukasa visits Ibuki's school afterwards and talks with Ibuki and Akira about three special scrolls. Meanwhile, after failing to rob Hibiki as he takes his leave, Daiki is forced into becoming Asumu's mentor.

Using Ryuki's powers, Decade battles Gyuki while Ibuki and Zanki argue whose fault this was. When Akira and Todoroki join the fray in their Oni forms to save Asumu as he tries to protect them, with Decade joining them by using Den-O's Ax Form, they manage to defeat Gyuki. He runs off before regressing to Hibiki, and Yusuke and Natsumi find him shortly after. Later that night, after talking to Asumu, Akira and Todoroki confront their mentors to put aside their differences, with Tsukasa supporting them. Ibuki and Zanki promote them to the role of new teachers of their respective schools. Meanwhile, Hibiki reveals the nature of Gyuki to Yusuke and Natsumi as Daiki arrives to claim the last scroll.

With their tour of the nine Kamen Rider Worlds complete, the Hikari Studio group returns to their home world, finding it as it was before the monsters appeared. Tsukasa is the only one who feels something is not right and questions the reason for the journey. Before Yusuke or Natsumi can attempt to answer, they encounter the violinist Otoya Kurenai, who thanks them for saving the world and tells Tsukasa that he earned a world of his own for his journey. As Natsumi goes out to see her TG Club friends and teacher for a high school reunion, Tsukasa and Yusuke have a short encounter with Narutaki who congratulates him on getting his own world.

After Tsukasa suddenly loses his powers, he learns from Kaito that he is actually in the World of Negatives. He later is seen by a talent agent and is offered to be signed onto his agency to become an idol. Although Yusuke acts as the voice of reason, he gets caught up in the fame seeking as well. Meanwhile, after her school friends return while waiting for Chinatsu, Natsumi that suggests that they should dig up the "treasure" they buried together, only to find that a parking lot was built over it and learning that Chinatsu moved their treasure prior. Once, Tsukasa finds Natsumi, he attempts to tell her that they are not in the real world, but Natsumi refuses to accept this as she runs off to the TG Club's hideout where she also meets the World of Negatives's Natsumi.

Arriving in Kaito's homeworld, the World of Diend, Tsukasa finds the world in peace and harmony, but with Kaito a wanted man. As Tsukasa assumes the role of a traveling salesman, he meets Kamen Riders Larc & Lance as they battle a Darkroach. After destroying the monster, Tsukasa learns that the world's residents kill Kamen Riders. As Tsukasa and company meet the head of area management committee, Junichi Kaito, Larc and Lance battle the Darkroaches until they receive aid from Diend. Saving them from reinforcements, Tsukasa learns from Haruka and Shin that the world is ruled by the mysterious Fourteen who uses his Roaches to manipulate humans.

Nearly killed by Lance, Kaito is spared when Larc stops her partner as he reminds her that he is the reason that Junichi is under Fourteen's control. After escaping the angry mob, parting from Haruka and Shin, Kaito and Tsukasa find Natsumi who tells them that Yusuke has been kidnapped by the Roaches before Junichi arrives. After remembering the events leading to his brother's enslavement, Kaito is reluctant to fight as he and Tsukasa transform to follow Junichi, leaving the brain-washed Yusuke behind and taking Natsumi to undergo the process as well.

Arriving in the new world with a strange card in hand, Tsukasa finds himself in the costume of a kuroko before running into Daiki who just stole a squid-like artifact. Daiki mentions that this world is not like the other A.R. Worlds before running off prior to the appearance of mysterious red fish-like monsters. Tsukasa is about to transform before several other Kuroko show up along with five young men and women who transform into the Shinkengers to fight drive them back into the Sanzu River.

After Tsukasa reveals himself, Takeru realizes that Tsukasa is the "Decade" Narutaki warned him about. Before the two can fight, Narutaki arrives to tell Tsukasa he is to blame for the terror brought unto the world by the Ayakashi Chinomanako who now has the powers of Diend, and that the only way to save the worlds he entered if he ceases to exist. After Takeru takes out the Nanashi and drives off Chinomanako as Shinken Red, Genta attacks Tsukasa believing that he is in league with Daiki until Natsumi takes him to the Hikari Studio, where Hikoma Kusakabe is hiding.

Tsukasa finds himself wearing strange clothes with another strange card as he, Natsumi, and Yusuke find themselves attacked by the Strange Demon Robot Schwarian and his Chaps as Kamen Rider Black RX battles them, with both sides believing Tsukasa to be Joe the Haze. When the Seamoon Fangire and Scorpion Imagin suddenly appear, Tsukasa becomes Decade to help RX out against the monsters with Agito's power as Schwarian runs off. After Natsumi stops RX from attacking Decade, RX takes her words to heart and sees Tsukasa as an ally.

Following Apollo Geist into another A.R. World, Decade is attacked by Kamen Rider Black until Diend arrives and summons Femme to hold him off. The next day, after learning that he is in the World of Black and seeing that he is on his own in saving Natsumi, Decade ambushes Guy as Ryuki and fights him until he uses a little girl as his hostage. When Decade takes a hit from Diend to save the child, Black watches and has second thoughts about him as Apollo Geist escapes.

Arriving in a new A.R. World, finding himself in a baseball uniform, Tsukasa notices the people are acting strange while saluting each other before he, Natsumi and Yusuke are singled out as rebels against Dai-Shocker with Propheta Cruentis, Go-Jaraji-Da, and Camponotus Worm Maxilla appearing to exterminate them. Amazon arrives to their aid, fighting the monsters with Decade backing him up as the people back up the surviving monsters under a boy named Masahiko.

Evading Apollo Geist and Llumu Qhimil with Diend's attempt to get the GaGa Armlet, Tsukasa has his wounds tended to by Natsumi in Dai-Shocker's school before Yusuke and a weakened Amazon join them, revealing that Masahiko took the GiGi Armlet as Ritsuko arrives and calls in the Dai-Shocker Soldiers after them despite Tsukasa questioning her faith in Dai-Shocker. Later after finding the Hikari Photo Studios in ruins, Amazon ponders if he should join them.

When Natsumi realizes that this is the world from her nightmares, she becomes wary for Tsukasa's well-being. Finding him in a tuxedo and feeling that this is the final chapter to their journey, they witness Wataru and Kazuma leading their respective Rider/monster groups against each other. After Rising Ixa and Leangle are killed off in the fight, Tsukasa makes his way to Wataru as he grieves over Ixa's death. Meeting the Fangire Queen Yuki, they learn from Wataru that the Riders are fighting each other to maintain the existence of their worlds.

After fighting off the Riders, Super Apollo Geist takes Natsumi to be his new bride as he flees. Kazuma Kenzaki appears, saying that Tsukasa's existence is the real cause of the worlds blending before confronting him as Kamen Rider Blade in King Form in order to force him to leave the world at once with Asumu keeping Yusuke and Wataru from interfering as Decade is easily defeated.