MegaMan X4 is the fourth game in the MegaMan X series(like the "4" in the name wasn't a hint?) This game is the first MegaMan X game where you play the whole game as either MegaMAn X or Zero. However, unlike MegaMan X5, you can't choose between the two at the start of each level, only at the begginning of the game.

Story

A mysterious man talks the leader of the repliforce to rebel against their human creators. Now causing havoc and getting ready for a war, the repliforce is mobilizing. X and Zero must stop the Repliforce, and a familiar evil.