I Became an Extra, and to Survive, I Must Kill the MC.

Jin Wei, a Mafia leader, dies during a gang war. However, right after his death, he opens his eyes and finds himself inside the body of a young vampire who came to Earth for exploration. As he accrues the memories of his previous owner, he realizes that he is in a novel world he used to read in his free time before his death. In this world, the MC considers anyone besides humans as evil. In the future, the MC will destroy the entire vampire race. Since Jin Wei was a vampire, he needs to do everything in his power to kill the MC, or he is screwed for sure. --- (Author's Note: Jin Wei is not a hero who will go around saving the world for justice. He is a villain that might destroy the whole world if he thinks it's necessary. Jin Wei will have a big harem as the story progresses. If you're not a fan of this type of MC and story, it might not be the right fit for you. Keep in mind that this is a work of pure fantasy, so our usual common sense might not apply to this novel.)