Aogami's somewhat robotic looks and mannerisms compared to other demons are a result of his artificial summoning method as a Proto-Fiend, where an artificial body filled with Magatsuhi to summon the power of a god into.
His appearance bears a near-perfect resemblance to that of Hayao Koshimizu.
Aogami starts the game as robotic in nature whose sole mission is to protect humanity, as well as rarely, if ever, emoting. His experience while merged with the protagonist has him learn more about humanity, their flaws, and capability to grow stronger and adapt. In regards to his relationship with the protagonist, Aogami only aids him because of his directive (i.e. protecting humans), but eventually comes to genuinely care for the protagonist's wellbeing, urging him to follow the path he believes in without any regrets. This also includes any path that runs counter to Bethel or Koshimizu's objectives.
He's naturally protective towards the protagonist, both partially because he's meant to protect humans and because he genuinely begins to care for him. As such, Aogami will do everything in his power to ensure the protagonist has the means to defend himself, even put them on the Throne of the Creator if he's willing to claim it.
"Young man, if you wish to live, take my hand."
—Aogami to the protagonist, Shin Megami Tensei V
Aogami is a mass produced Proto-Fiend model created by Bethel Japan to show that they can still fight, in spite of most of its gods bar one being forced into hiding due to having their power depleted in Armageddon.
Aogami is an amnesiac entity that appears before the protagonist while he's being attacked by Daemons, destroying much of the horde during his entrance, and the two fuse together to become a Nahobino, a condemned being, in order to survive. While fused, Aogami guides the protagonist by voice, acting as a field guide and offers advice when dealing with demons, and warning him of the presence of particularly strong demons, as well as a telecommunications relay.
Aogami was present for the appearance of Lucifer when the forces of chaos and Bethel led by Abdiel clashed at Tokyo Tower within what would be later called Da'at 18 years ago, and went dormant after Lucifer scattered himself to the winds, reactivating years later when the protagonist was attacked.
Much later on, it was revealed that Aogami's true identity is Susano-o. A member of Bethel, his memory data was badly damaged in the war between Lucifer and the angels, leaving him largely amnesiac. His true self is hinted at by how the protagonist develops largely water and lightning-based abilities as a Nahobino, and the fact he shares his blue hair color and clothing color palette with Amanozako, his daughter. During the final ascent into the throne, Tsukuyomi refers to him (and his Nahobino hybrid with the protagonist) as a brother before telling them that he will show them no mercy.
Endures lethal attack and fully heals HP once in battle.
Aogami lands before the protagonist.
Aogami asks the protagonist to take his hand.
Although his name is written in katakana, Aogami could mean "blue deity" (青神*)? in Japanese, as ao and gami respectively translate to "blue" and "deity." However, there is not a specific god in Shintoism that bears the name of "blue deity." Aogami could also mean "blue hair" (青髪*)? in Japanese, which matches the hair color of Aogami and his Nahobino form with the protagonist.
In Other Languages
青神 (Qīng shén)
The glyph on Aogami's chest resembles the vowel "u" of Siddhaṃ script. It's technically an S, for "Susano-O".