The world faces a constant threat of unknown origin, the Darkness. Normal weaponry and tactics are useless against them. However humanity has found its weapon to fight the monstrosity: The Vampiress. Formerly ordinary girls who've gone through an unknown evolution that allows them to use magic and convert normal humans into Blood Warriors. Mutsuroku Academy is a education institute on a artificial island to train the Vampiress and their Blood Warriors.

Kotaro is a student within this academy, and is a Blood Warrior who fights without the aid of a Vampiress. Join him as he searches for his missing sister, makes friends, enemies, and rivals.

Throw in some Vampiress Hunters and a mysterious organisation with an unknown objective, welcome to Love Thy Vampiress.