Slash Beast of Repliforce, gives Twin Slasher to X, and Shippuuga to Zero is weak to Ground Hunter/Raijingeki.Jet Stingray of Repliforce, gives Ground Hunter to X, and Hienkyaku to Zero is weak to Frost Tower/Hyouretsuzan.Frost Walrus of Repliforce, gives Frost Tower to X, and Hyou retsuzan to Zero is weak to Rising Fire/Ryuenjin.Magma Dragoon of the 14th Special Unit, gives Rising Fire to X, and Ryuen jin to Zero is weak to Double Cyclone/Raijingeki.Storm Owl of Repliforce, gives Double Cyclone to X, and Tenkuuha to Zero is weak to Aiming Laser/Rakuhouha.Cyber Peacock, gives Aiming Laser to X, and Raku houha to Zero is weak to Soul Body/Ryuenjin.Split Mushroom, gives Soul Body to X, and Kuuenzan (as well as Kuuenbu) to Zero is weak to Lightning Web/Raijingeki.Web Spider of Repliforce, gives Lightning Web to X, and Raijingeki to Zero is weak to Twin Slasher/Shippuuga.This immediately causes the entirety of Repliforce to be labeled as Mavericks by the human government, forcing the Maverick Hunters to turn against them and obstruct their migration. This incident is the last straw, and the head of Repliforce, a giant Reploid named General, launches a coup d'état to start a nation only for Reploids in space. However, Colonel refuses out of pride and contempt for human government.
One day, the aerial city Sky Lagoon is sabotaged by Mavericks, causing it to crash to the ground with Repliforce suspiciously in the area, the Maverick Hunters request Colonel disarm his men and come in for questioning. This controversy creates tension between Zero and his sweetheart Iris, who is the sister of Colonel, an influential leader in Repliforce. However, they consistently fail to protect humans, causing humanity to distrust them and their military might. In the year 21XX, years following the Doppler rebellion, a global Reploid military called "Repliforce" is formed to help combat the constant Maverick uprisings. Mega Man X4 is the fourth entry in the Mega Man X series, released on the Sega Saturn and PlayStation on August 1997 in Japan, September 1997 in North America, and October 1997 in Europe.