Jack the Ripper is Humanity's representative in the fourth round of Ragnarok, going up against Heracles. Jack is also the main character of his spin-off manga, "Jack the Ripper's Case Files".

Jack is a serial killer hailing from late 19th century Britain and is a very important figure in the history of London, being considered "Humanity's Most Infamous Serial Killer" (人類史上最も著名な殺人鬼, Jinrui Shijō Mottomo Chomeina Satsujinki).