Akuma no Riddle  

AnR, Riddle Story of Devil, 악마의 리들, 恶魔的谜语, 悪魔のリドル

Tokaku Azuma has recently enrolled at Myoujou Academy, a prestigious all-female boarding school. However, there's a twist: she and 12 other students in Class Black are participating in an assassination challenge to kill their classmate, Haru Ichinose. The winner will receive their heart's desire, no matter how difficult or costly it may be. Each assassin only gets one chance; if they fail, they will be expelled. Despite the tempting reward, Tokaku chooses a different path. Although she is tasked with killing Haru, Tokaku finds herself drawn to her classmate and decides to protect her from the growing bloodlust of their fellow assassins.

Akuma no Riddle is based on Yun Kouga and Sunao Minakatas manga series of the same title. Despite premiering while the manga was in the middle of publication, the anime adapts the full story of the manga, with a few additions and alterations.