It's been many years after Sigma's last appearance, and things have been going relatively peacefully for the Maverick Hunters. Aside from the occational Maverick out-break, things are going good. Needless to say, Sigma decides to crash in on the party. X and Zero are rushed into action to stop him as quickly as possible.
     X and Zero manage to stop the maniac, but in the process they release the deadly Sigma Virus on the earth (completing Sigma's new plain). The Sigma Virus is the program that causes the Reploids to go Maverick. Also, the space station, Eurasia, has sustained severe damage from the battle with Sigma and his on a collision course with earth. X and Zero have 16 hours to stop the station. Get to work!
     For some reason beyond the logical, Capcom has chosen to name the bosses of the game differently in the instruction menu. I have no idea why they did this, but I have provided both names for every character. There isn't really a set order in Mega Man X5. The enemies are easy enough that if you're a candid Mega Man X player you could easily defeat them all with the X-Buster, but here's the enemies by weakness anyway.
The order of bosses by weapon weakness:
   1. Crescent Grizzly (Grizzly Slash)
   2. Tidal Makkoeen (Duff McWhalen)
   3. Volt Krakken (Squid Adler)
   4. Shinning Hotarunicus (Izzy Glow)
   5. Dark Necrobat (Dark Dizzy)
   6. Spiral Pegacion (The Skiver)
   7. Burn Dinorex (Mattrex)
   8. Spike Rosered (Axle The Red)