Enigma

Enigma, stylized as ǝnígmǝ 【エニグマ】, is a Japanese manga series written and illustrated by Kenji Sakaki that appeared in Shueisha's Weekly Shōnen Jump magazine since September 2010.

Plot
The story opens with Sumio Haiba to the rescue again with his Dream Diary Ability, this time saving a girl from harassment at Yūyami High. On his way home from school that day, he notices ǝnígmǝ for the very first time on a television screen on the street. That night, his mother Mina realizes this and rushes off to work. Sumio predicts her being captured by ǝnígmǝ, but ends up being too late to save her.

After making a promise the next morning to get his mother back and going to sleep, Sumio winds up trapped inside Yūyami High with six other Yūyami High students, including childhood friend and classmate Shigeru Kurumiya. It is at this point that ǝnígmǝ formally reveals itself, whom introduces the seven to a mandatory aptitude examination on their true natures known as an e-test, the fifth of its kind. The e-test rewards participants with their deepest desires as determined by ǝnígmǝ should they finish. Should they not, they shall remain trapped inside ǝnígmǝ's world as a Shadow forever. For the next 72 hours, the seven are trapped inside the school and must find their way out by finding seven "Passwords" around the school for each to use on a locked "Exit" door. However, there are Shadows roaming around the hallways, ready to kidnap and take control of any stranded, careless participants.