Chaos Son

When a female otaku gets into a bus accident on her way to work, she wakes to find herself in the body of Remus Ford; the stepfather to Siegfried Nightvale, who's the villain and rival to the hero in a popular web novel. After she reincarnates as him, Remus begins to work hard to be a good father to Siegfried. However, when the source of Siegfried's powers is obtained, Remus leaves for seven years so Siegfried can train on his own without him being an obstacle like in the story. But with Remus bonding to him and then leaving, it changes Siegfried's outcome to what he's supposed to become in the future.