Despite the name this is actually a Mega Man 2 hack, which translates it back into Japanese and adds a ton of cool features. To put it simply, this is a new Mega Man 2, the only things that still exist from the original are the robot masters, and even they’ve been changed in terms of fighting style.
Don’t take anything for granted in this hack, those weak rabbit robots in Wood Man’s stage? They shoot instant death fireballs now. Sniper Joes? In addition to their normal fighting style they also fire Crash Bombs are you!
It should also be pointed out that the music has been changed, this is very rare in ROM hacks, it seems some of it comes from the Game Boy Mega Man games and some comes from other NES titles.