Tokaku Azuma wird in die Schwarze Klasse der Myojo-Akademie versetzt. Sie wird eine Assassine – eine Killerin, so wie alle ihre Mitschülerinnen in dieser Klasse. Aber sie ist anders als die Anderen.
A skilled assassin named Tokaku Azuma is transferred into Myōjō Academy's "Class Black", tasked with identifying and killing a target amongst her twelve classmates, the rest of whom are also assassins. At her first homeroom class, consisting of five of the total 13 students, Tokaku finds herself drawn towards a kindly girl named Haru Ichinose, believing she may be the target. As Tokaku spends more time with Haru, who is revealed to be her roommate, she notices some knife wounds on her legs. After encountering her various classmates throughout the evening, Tokaku, who had also been tasked by her teacher, Kaiba, with solving a puzzle reading "The world is filled with (___)", becomes bewildered when Haru suggests "forgiveness" as an answer.
Tokaku Azuma est transférée dans la dixième classe Noire de l’académie Myojo, un internat pour filles, pour une mission d’assassinat. Sa cible, qui est aussi celle de ses camarades de classe, tous assassins, est Haru Ichinose. Mais Tokaku est troublée par la jeune fille et semble se poser des questions sur sa mission.
ミョウジョウ学園10年黒組、ついに開講。
お互いの素性が伏せられた中集められた暗殺者12人と、ターゲットである1人で始まる学園生活。
東のアズマ”と称される一族のエリート暗殺者、東兎角、そして自分が標的と知りながら、生きて卒業するという強い意志を持った一ノ瀬晴。
学園の寮で、この二人が同じ部屋になり…!?
묘죠학원 10학년 흑반, 드디어 개강. 서로의 정체가 감추어진 상태에서 모인 암살자 12명과 타깃 1명으로 시작하는 학원생활. 동쪽의 아즈마라고 칭해지는 일족의 엘리트 암살자, 아즈마 토카쿠. 그리고 자신이 표적임을 알면서도 살아서 졸업할 것이라는 강한 의지를 가진 이치노세 하루.
학원의 기숙사에서 이 두 사람은 같은 방이 되고...
Un asesino experto nombrado Tokaku Azuma se transfiere a Myojo Academia de "Clase Negro", la tarea de identificar y matar a un objetivo entre sus doce compañeros de clase, el resto de los cuales son también asesinos.