This manga is about a war between humans and demons. In Devilman these demons were the dominanting species living on earth before humans. They are suddently trapped in ice during an ice age, without demons to prey on humans, humanity is able to develop into current society. Devilman's plot starts when demons are discovered to be alive in the ice, and start a war against humanity, since they ruined earth's balance with nature and, well, because they're demons.
The main character is a schoolboy named Akira who is induced by his friend to willingly get posessed by a demon. Due to his pure heart, Akira is able to maintain is human heart and control and promises to protect humans from demons.
The art is amazing, the panel layouts are stunning and there are several moments when suspense is maintained simply by this, rather than the plot.
The story is interesting altough having some confusing aspects, the rythm in particular was somewhat chaotic, particulary towards the end. One of the most interesting aspects of the storytelling, wich I believe to be typical of this period, is a build up of tension not with the major plot, but with small action sequences. It also has a surprising progression, since it goes from a typical "special schoolboy with secret powers fighting goons to protect loved ones/humans" to a apocalyptic/post-apocalyptic/dystopic situation, cold-war/noir style story, where the central concept focuses on what being human is.
Nagai is also well known for his use of gore, and he really uses it well in Devilman. Since those moments are scarce they really cause an impact.
The conclusion itself is very interesting and original, even tough the final twist is the weirdest and most pointless one I have ever seen.
