If you're looking for manga similar to Rockman 4, you might like these titles.
An unknown alien enemy attacks the Earth and the armies on Earth must try to hold off the invasion.
After taking down Dr. Wily's previous attempt at conquering the world, he's back to his old tricks and yet again, it's up to Rockman to foil his plans!
Meet Kyosuke Nanbu and see how one man, this one man is pulled into a fate that involves politic conspiracies, military weapon development run conflicts, betrayals, revolts, people with super natural powers & an enemy extra terrestrial invading menace. Even though he is just a "regular human", Kyosuke is to the core a brave man who will not be shunned "so easily" and at the command of his own trademark machine, the so called old fashioned "Alt Eisen" he will lunge towards the center of the conflict and will blow away everything that stands in his way.
Lan and his Navi Mega Man live in a strange city where everything is connected by a network. With the help of their friends, they will face the mysterious Dr Willy who is trying to sow chaos in the city with its diabolical virus.