Devilman features Akira Fudo, a shy and timid teenager who has gone mountain climbing in the Himalayas with his father. While in the middle of the expedition, both father and son are killed in a tragic accident. Akira's body is found and possessed by the demon soldier Devilman, who uses his new human form as a disguise in order to fulfill his mission of causing chaos on Earth in order to pave the way for a demonic invasion of the planet.

Before his mission can begin in earnest, Devilman meets Akira's childhood friend Miki Makimura and quickly falls in love with her. Devilman resolves to protect Miki and humanity as a whole by battling against his fellow demons. Demon Tribe leader Zennon becomes greatly angered at Devilman's betrayal and is quick to send Devilman's former comrades to destroy him. The other demons soon learn that Miki is precious to Devilman and he must now work to protect her, as well as protect himself. Will the power of love be able to overcome that of true evil?

The heroes of the series Mazinger Z and Devilman fighting against the evil Demon Clan.

Akira is just another normal kid in modern-day Tokyo, until an old friend of his, Ryo, shows up and turns his world upside down. Akira learns that there is an upcoming war of demons on humanity and he has just been enlisted for a major tour of duty. But the only way to fight a demon is with their power, so Akira and Ryo risk a dangerous ceremony in an attempt to create humanity's only hope: the powerful Devilman.

Demons exist and their power is beyond what humans can fathom. In fact they are so strong that humans do not stand a chance against them in a fight.

The only thing strong enough to defeat a demon is another demon and it is trough this logic that Ryo Asuka hatches the plan to have his good-hearted friend Akira Fudo possessed by a demon. If a person is of pure of heart then he might be able to control the demon that posses him and thereby acquire power equal to a demon. After raising some hell in a club the plan works and Akira is possessed by the powerful demon known as Amon.

Now Akira is humanities sole champion of justice against the hidden demon menace that has plagued humanity since the dawn of time.

[Source: Anime News Network]

Summary of the 1972 Devilman series.

Fear runs rampant throughout Tokyo with the revelation that demons in fact exist amongst us. Paranoia and the darker side of humanity boils onto the streets as people turn on one another, suspecting that anyone could in fact be a demon hiding in human clothing. Amidst the growing tensions, tragedy strikes Akira causing his mind to snap, retreating into his subconscious, allowing his Devilish alter-ego Amon to break free from Akira's cage of flesh and wreak havoc on both human and demons alike.

In the new film, the two title characters will meet and battle because of a certain incident. The tagline reads, "Who will survive…?"

[Source: Anime News Network]

Our protagonist Akira Fudo hears from his best friend Ryou Asuka that the demons will revive and reclaim the world from humans. As humans have no chance against the demons' power, Ryou suggests combining with a demon. Akira becomes Devilman, a being with the power of a demon and the heart of a human.

[Source: Anime News Network]