Other Worlds; Seraph of the End

In this world the same situations occured, this time Mikaela Hyakuya and Yūichirō Hyakuya have never met, not only that but Yūichirō lives underground. A secret underground society that was already under the earth's surface by the time the demons and the Four Horsemen of John started appearing and taking over the city.

Mikaela an orphan and Yūichirō a boy that got lucky around the time of the apocalypse.