Upon arriving in the World of Agito, Yusuke is shocked that there are Grongi in the world which are being dealt with by Kamen Rider G3-X. He is further shocked when he sees an interview with Toko Yashiro, who is physically identical to the Ai Yashiro that died back in the World of Kuuga. Arriving at the police station, Yusuke offers to be the new user of the G3-X suit, but loses the position to Kaito. While this occurs, finding himself in a mailman outfit with a letter to Shouichi Ashikawa, Tsukasa and Natsumi find the man before they are attacked by what they think to be a Grongi. But during the fight, Tsukasa realizes he is fighting an Unknown, an Ant Lord called Formica Pedes.

After Yusuke saves Tsukasa from Delta's attack, Gills is about to fight when he's overcome with pain as the Unknown shows up to kill him. As Shouichi escapes, Toko recognizes him via G3-X's camera. While Tsukasa insists on protecting an annoyed Shouichi, Yusuke reports the defeat of the Grongi and the emergence of the Unknown. He finds Toko saddened, but has little time to help her as Kaito takes the G4 chip stored within his locker. Yusuke demands the chip back, but during the struggle, Toko blasts the chip to bits and a disappointed Kaito leaves. The next day, as Tsukasa continues to keep Shouichi safe from the Unknowns' attack, Yusuke learns that Shoichi was the original user of the G3 suit when he receives the letter for Shouichi from Toko.