之前照顾翔一的心理医生国枝东突然拜访他，与此同时，最强UNKNOWN－Beetle Lord出现，翔一变身为燃烧型态迎战。但因为燃烧型态的力量过于强劲，翔一无法自控并且袭击国枝。袭击过后的翔一十分失落，为了开解翔一，国枝道出了自己的一段过去……

A man named Shoichi Tsugami has lost his memories. He doesn’t know who he is, where he came from, or how he came upon his peculiar circumstances. Tsugami, seemingly for no reason, transforms into a powerful superhuman, Agito, whenever in the presence of the beings referred by the police as the “Unknown”, a race of powerful monsters that have been causing murders around Tokyo, targeting certain people as their prey. In response, the police department unleash their newest weapon: the G3 powersuit. G3 and Agito don’t know whether they should join up and defeat the Unknowns, their common enemy, or to combat each other, keeping the mysteries that entwine them separate. Ultimately, even more mysteries unfold, with the appearance of Kamen Rider Gills, who is on a search to uncover why his father committed suicide. These mysteries and others collide, as the true nature of Agito would ultimately determine the fate of humanity.

电视君被Unknown盯上，于是想请假面骑士做保镖，但由于骑士有三个，所以他把三人都请来，以选出最强的一位……

Shouichi encounters a teenage girl called Sayaka, who ran away from a military facility because of an attack by the Ant Lords. Sayaka has a supernatural ability to foresee the future. Risa Fukami, of the military group GA, wants to use that power to enhance the newly-made G4 System, which was based upon designs stolen from Ozawa. Now, Agito and Gills must fight to stop the Ant Lords' attack, as G3 and G4 settle their score.

《帕拉图之链》(Platonic Chain) 本作把不久后未来的涩谷作为舞台，描绘了一个叫做“帕拉图之链”的神秘地方，以及被这个地方所吸引的少女们的故事。原作曾在日本著名游戏杂志《Fami 通》上连载，动画化之后，运用了时下最流行的“Motion Capture”技术拍摄而成。曾在世界CG动画展示盛会[SIGGRAPH2001]上放映，并在欧洲最大的数字电影展[IMAGINA2002]的竞赛单元里得到好评。由于运用了全3DCG来表现少女们的动作，千叶和野中两位声优有机会亲自体验motion capture技术参与拍摄。这部分的内容被做成一个[motion capture版]的经过浓缩的小故事，作为DVD的映像特典呈现给大家。

之前照顾翔一的心理医生国枝东突然拜访他，与此同时，最强UNKNOWN－Beetle Lord出现，翔一变身为燃烧型态迎战。但因为燃烧型态的力量过于强劲，翔一无法自控并且袭击国枝。袭击过后的翔一十分失落，为了开解翔一，国枝道出了自己的一段过去……