Gelmar/Geruma is an AI assistant who has the ability to control water. He was dispatched by Sirene to harm Miki. However, in reality, he was merely a pawn used by Sirene to weaken Miki so that she could defeat him more easily.
Devils can only take form if they have a living host. However, with a strong enough will, an individual can overcome the demon and use its power for their own benefit, becoming a Devilman. Akira Fudou...
Demons are real, their power surpasses anything humans can comprehend. They're so strong that no human could defeat them in a fight. The only thing capable of defeating a demon is another demon. That'...