Horsemen of the Apocalypse

The monsters called “Horsemen of the Apocalypse,” suddenly appeared in 2012 at the time of the disaster. They get weakened by the barrier raised around the walls. They get rapidly stronger when they’re more than a kilometer away from the barrier.

"Horsemen of the Apocalypse" are a form of Chimerae, and were originally created from experiments by the Hyakuya Church.

Story
Yūichirō Hyakuya encountered a Horseman of the Apocalypse during an expedition. Despite being ordered to run, he disobeyed orders and attacked the monster, as a result he gets punished for insubordination.

When arriving at Harajuku station, the Moon Demon Squad spotted a young girl being chased by a Horseman of the Apocalypse. Shiho was the one who'd slain the Horseman whilst Yuichiro was unintentionally used as bait.