Rockman Complete Works: Rockman 5 - Blues no Wana!?

Mega Man 5 takes place during the 21st century, about two months after the events of Mega Man 4, when the mad scientist Dr. Wily once again attempted to take over the world.[2] Proto Man, secret brother and once ally to the world's greatest hero Mega Man, apparently leads an army of robots in a series of destructive attacks on the world. To cripple the world's defenders, he kidnaps his own creator, the genius scientist Dr. Light. As Mega Man witnesses his creator's kidnapping, he's confused, wondering why Proto Man is doing this, but with little choice left, he sets out to stop him, assisted by Beat, a robot bird that Dr. Cossack gave him as a gift. With Dr. Light gone, Dr. Cossack now assists Mega Man from the sidelines for the occasion, and he powers up the charge shots of his Mega Buster and sends him Beat to help him on his battles to save Dr. Light.

Mega Man prevails over a new group of eight powerful "Robot Masters" working under Proto Man: Star Man, Gravity Man, Gyro Man, Stone Man, Crystal Man, Charge Man, Napalm Man, and Wave Man. He then makes his way to Proto Man's fortress, where he has to fight against the four Dark Men, new robots designed to destroy him, and he defeats the first three, but the alleged Proto Man ambushes Mega Man and nearly kills him. However, a second Proto Man arrives just in time, revealing the first as an imposter: it's the fourth Dark Man. After defeating the final Dark Man, Mega Man finds out that Dr. Wily was behind everything: two months earlier, Proto Man had ruined his most recent evil plan, as he had rescued Dr. Cossack's daughter Kalinka, who Wily had kidnapped to blackmail Dr. Cossack into working with him in order to destroy Mega Man. Wily was furious, and in retaliation, he created Dark Man to frame him for his robot's crimes, including the kidnapping of his own creator.

Mega Man pursues Wily to his newest hideout, defeats him, and saves Dr. Light. However, the fortress begins collapsing, and while Mega Man is distracted from holding up the ceiling from crushing him and Dr. Light, Wily manages yet another retreat. Just after Wily escapes, a familiar whistle is heard, and part of the ceiling is blasted away, allowing Mega Man and Dr. Light to also escape. As the two watch the castle collapse from a distance, their mystery savior is revealed to be the real Proto Man, who quietly slips off unnoticed.