Demon Armor Reincarnation ~ The Transformation Hero of Another World ~ [Incomplete]

I was an ordinary student when I was caught up in a convenience store robbery by chance and died. When I next awoke, I had been reborn into a world of swords and magic as a "Demon," a contractor of the sentient magical armor Foil. What are magical armor and demons? Why was I reborn as a demon? To solve these mysteries, I hide the fact that I am a demon and set out on a journey to defeat the Demon King alongside a girl called a "Hero," Rilka. *Some of the characters in this work are fictions based on historical facts.