Started reading Zetman after seeing the anime promo image; c'mon, look at the potential fanservice! It's one of those gritty shounen manga aimed at the male population. I've never read any US comics, so while this background story sounds sorta like a superhero (Batman-like) story, do US comics show as much blood and guts that manga does? Anyway, there are two main male leads in this story; one created with supernatural powers who tries to help people for money, and one rich-boy character who was influenced by anime and fights for justice with technology. There are a couple time skips in this manga each with some fairly violent events that shape the boys. The female characters aren't treated really well, so beware of fairly graphic scenes depicting well, crimes against young female students and at least one prostitute.
Basically, some mad scientist try to create perfect humans in a lab and end up creating 'Players', humanoid-type beings who transform into monsters. Jin/Zetman was the only perfected experiment, and so on. Masakazu Katsura is the mangaka whose only other work I know is DNA^2...and hey, character designs for Tiger & Bunny. The development of the two boys take up almost 12 volumes. Then, it seems they have their posse of supporters and direct their energy into facing Players. And the potential fanservice part is...that they aren't rivals or enemies at that point and hold some sort of admiration for each other. Anyway, if you could stomach manga like Claymore or anime like Rainbow, feel free to check this out. I have a feeling that the anime's story might be slightly edited.