Life could be better for shy, anxious university student Rin. The apartment she has rented is hardly the sunny palace the rental listings suggested. The housing complex is rundown, grim and haunted by troubled souls lurking in dark corners. Ghastly crimes are occurring in the vicinity. And a grinning stranger makes his unsettling presence known. Beyond all this, Rin is coming to realize that something even more sinister is manifesting itself, something at the cursed crossroads of mythology, monstrosity and medical science. Determined to find out more, Rin visits the library, where she meets a sympathetic young staffer. But what she learns does not begin to put her mind at ease.

"I'm going to live for myself!" The greatest assassin on Earth knew only how to live as a tool for his employers—until they stopped letting him live. Reborn by the grace of a goddess into a world of swords and sorcery, he's offered a chance to do things differently this time around, but there's a catch...He has to eliminate a super-powerful hero who will bring about the end of the world unless he is stopped. Now known as Lugh Tuatha Dé, the master assassin certainly has his hands full, particularly because of all the beautiful girls who constantly surround him. Lugh may have been an incomparable killer, but how will he fare against foes with powerful magic?

The story takes place in Tokyo Butei High School, a special school where armed detectives—"Butei"—are trained to use weapons. Kinji Tooyama is a second-year-student who has a special ability, but he keeps it a secret to maintain an ordinary, peaceful life; however, when he gets caught in a bombing on the way to school, he encounters H. Aria Kanzaki, the most powerful S-Rank Butei student in Assault Studies.

Subaru Sumeragi is the 13th head of the Sumeragi Clan and a most powerful onmyouji. Subaru is hired to exorcise a construction site, but his employer mysteriously died. The only suspect is a man who repeatedly walks away from situations in which he should have died. Then Subaru meets a young woman intent upon cursing the man, saying that he killed her brother. Subaru must figure out how his employer died and fight the evil spirits that are protecting the man with the help of his friend and twin sister, Seishirou Sakurazuka and Hokuto Sumeragi.