Per wiki policy, Spoilers Off applies here and all spoilers are unmarked. You Have Been Warned.
Gene learned how to kick ass from a practitioner of Hokuto Shinken
Specifically, it was Jagi. Respecting Gene's inner Jerkass, they developed a certain kinship and taught him how to fight like a cheating bastard. However, they had a falling out (IE Jagi tried to kill Gene for reminding him of Kenshiro) before Gene had an opportunity to learn the really deadly stuff. The original user of the God Hands real name is "Alexander"
Yes, I know its a reference to a Mike Tyson quote, but it would work. If there is ever another God Hand game, it will be a prequel and star Alexander
The game is a partial reimagining of Berserk
Consider this: God Hand's setting is similarly crappy to Midland: Demons run around, Powerful warriors sell themselves to become even stronger, and the Evil Five-Man Band is working for an even WORSE villain. Gene is Guts, Olivia is Casca, Azel is Griffith, The Four Devas are essentially the Godhand and Angra is The Idea Of Evil. The only things that changed are that there's a lot less Grimdark, a ton more Camp and The Eclipse didn't exactly happen. The God Hands were originally broken off arms from Asura
Considering they're both from the same company, it would be insanely awesome in a future Capcom vs. game to have Asura and Gene fight each other. The Psychic Midget is full of shit.
He calls on mooks to attack you during the battle. He has a clear affiliation with the demons, he's just putting on a paranoid shtick because he's an asshole. Elvis' cigar is a Power Limiter, and demons are less vulnerable to dying in their human form.
He only throws it away shortly before transforming into Demon Elvis, and dies following that battle. Belze also goes down after a single battle with Gene, while it took three for Elvis and two for Shannon, leading to the possibility that especially powerful demons such as the Four Devas are much harder to finish if they stay in their human form. The dogs you encounter in the game are people Shannon transformed.
She does the same thing to you during her boss fight, but you manage to shake off her magic after a few moments. It might have a stronger effect on regular humans who don't have a God Hand.God Hand takes place in a genuine After the End type universe, fought with Fantastic Nukes that altered the laws of reality as we know it.
The world of God Hand is mostly apocalyptic, except for a few sanctuary cities, and Stage 5 is an example of one.