Akira had dark black hair with a blue tint, with sideburns, he had brown eyes and by the time of the second OVA he had a rather muscular physique. As Devilman he became somewhat larger than a normal human, he grew large bat like ears with a red crest at the front of his head and a pair of antenna. He had marks above his shoulders and grew black fur and a tail below his waist line.
Akira had large bundles of strength and claws to match for close combat as well being a great fighter, he could fly and emit beams from his forehead. His antenna were capable of discharging electricity.
Before his transformation, Akira was a kind and timid boy but would show a face of bravery when it was called for. Afterwards however he became a whole lot more brave and confident, and in some cases perverse. He had romantic feelings for his friend Miki and was best friends with Ryo Asuka.
He also believed outright in the good of humanity, before the same people he was fighting for killed Miki. Eventually allowing for the demon Amon to temporarily take control.
Akira had a pretty average life, despite that his parents where killed by demons Akira still studied and even got a girlfriend, however Akira's life changes, when his old friend, Ryo backs. Ryo tells Akira that demons are real and will attack humans, Akira and Ryo aren't powerful enough to kill demons, so the only way to destroy a demon is to become a demon. Akira takes a part in sabbath, every single human who was on the sabbath turns into demon, however when the demon named "Amon" tries to posses Akira, he fails, Akira takes control and becomes Devilman.