Ayumu (アユム) is a mysterious boy, implied to come from a despaired future, who travels to the human world in search of Takeru Tenkūji. He appears from a golden Gamma Hole resembling one used by someone with a connection to the Great Eye, searching for something with the power to change the world. He finds Kamen Rider Genm attempting to trigger the Shakiriki Sports Gashat, pulling it out of his hand, curious how it could have the power he was seeking. Genm tries taking the Gashat back by force, but Makoto and Alain (as Specter and Necrom) arrive and fight him off. Ayumu says he is looking for Takeru; taken to the Daitenkū-ji, he shows rather extensive insight into events of the recent past and the future. He questions the usefulness of Takeru's decision not to remain as a ghost, constantly repeating how hopeless the future is and how people can't change it, and later expressing doubt that only Makoto, Kanon, and Alain can fix the Gamma World.
Takeru tells him how peoples' connections with each other will branch out and allow them to change the world, but Ayumu runs off, encountering strange boxes and a group of Bugster Viruses. Takeru (as Ghost) and an arriving Ex-Aid defeat the Viruses, before jumping in to protect Ayumu from an energy blast attack by Genm. The attack knocks away the Shakiriki Sports Gashat, which Genm retrieves before departing. Ayumu continues to deny peoples' ability to change the future, how those who can help won't always be around, but Takeru says that their feelings have connected and will always be with him, that this is the power to change the world, and that he believes in Ayumu's power and humanity's potential. Seemingly convinced, Ayumu steps away, reaffirming his resolve before a golden Gamma Hole appears behind him. He steps backwards into it, thanking Takeru and whispering the word "dad", which implies Ayumu could be Takeru's son from the future.
Ayumu is portrayed by Shouta Ikoma (生駒 星汰 Ikoma Shōta)