Mega Man vanquishes Dr. Wily and the six robot masters he stole from Dr. Light. However, instead of giving up and reforming, Dr. Wily plots his revenge against Mega Man with eight robot masters of his own creation - Air Man, Quick Man, Flash Man, Heat Man, Metal Man, Bubble Man, Crash Man and Wood Man. Unlike their predecessors, the new batch of robot masters were meant for combat from the get-go and were not meant for industrial purposes.
The persistent Dr Wily would then deploy his troops in an attempt to conquer the world. Mega Man gets an assist from Dr. Light to combat this new menace through the development of vehicles 1, 2 and 3. The vehicles help Mega Man avoid enemies and obstacles as well as reach areas he normally could not.
Dr. Light also developed the energy tank which allows Mega Man to replenish his health in one fell swoop. He can carry four of these at any one time. These tanks would be a staple in later games. This would make the game a bit more forgiving than the first game where the margin of error is very slim.
Mega Man 2 is the debut of the Wily Castle. While Wily does have a factory in the first installment of the game, nowhere in the game does it show a castle. In the wily castle would be the first "rematch room" which contains teleportation pods which lead to the robot masters' chambers. The matches are much easier however, since you already have the complete set of weapons and could easily use each robot master's weakness against him.After you vanquish the robot masters a second time, Wily appears in a new crazy contraption to stomp Mega Man. After you trash Wily's newest toy, you would follow Wily into an underground cavern where Wily would seemingly transform into an alien. Was Wily an alien all along or is Wily collaborating with aliens to conquer the world? Beat him to find the answer.