Eida is a soldier of A.I.M.S. tasked with hunting down any remaining active HumaGears and a supporting antagonist in Kamen Rider Zero-One. He is armed with a RaidRiser that allows him to become the Invading Horseshoe Crab Raider.
He is portrayed by Ryuma Hashido.
After Zaia Enterprise acquired Hiden Intelligence and began using A.I.M.S. to deactivate all remaining rogue HumaGears, Eida and his partner Ono were sent alongside Captain Yua Yaiba to terminate Izu after she was reactivated by Aruto and Jin. However, the two Riders, with backup from Isamu Fuwa, were able to defend Izu and drive off A.I.M.S.
After Aruto had opened up a new company to repair the HumaGears ZAIA had deactivated, Gai Eida and Ono accompanied Gai when he went to shut it down. Assuming their Invading Horseshoe Crab Raider forms, Eida and Ono assisted Thouser in fighting Zero-One and managed to overpower him. As they prepared to finish off Aruto with a combined attack, Jin Burning Falcon appeared to provide backup to Aruto and forced the three to retreat. Later, the two accompanied Yua Yaiba in a mission to shut down the rogue HumaGear G-Pen, but were ordered to stand down and not attack him by Yua, who instead let him escape. Later, the two accompanied Gai after he decided destroy G-Pen himself, but were defeated again by Zero-One MetalCluster. Eida and Ono tried to help their boss up, but Gai angrily brushed them aside.