Under Night In-Birth

Once a month, the Hollow Night descends on the city. Invisible creatures called Voids emerge and feed on a power called EXS, attacking anyone they encounter. Those who die or are fully consumed become Voids themselves. Those who survive become In-Births — humans who can now control EXS. High school student Hyde Kido survived and gained the power to summon Insulator, a sword capable of killing In-Births. A girl named Linne — immortal and willing to train him — agrees to teach him, on one condition: when he is ready, he will end her life. Multiple factions are vying for control over EXS. Hyde is now one of them.