Riddle Story of Devil

The story is set at Myoujou Academy, a private girls' boarding school. The 10th year's Kurogumi class has 12 assassins with their sights on one target, Haru Ichinose. Tokaku Azuma is a recent transfer student who is also targeting Ichinose, but she gradually develops feelings for Ichinose.

(Source: Anime News Network)