The 2040 global pandemic infected 100 million people and left 80 million dead according to the 2050 report done by the World Health Organization (WHO). With the extreme number of children that were lost during the crisis, the government passed the Child Protection Law to protect and educate the hope of the human race. All children were given a bracelet called the “monitor,” to ensure their lives were safe, healthy and productive.

In a society where online relationships are more common than face to face conversations, three classmates, Hazuki, Ayumi and Mio become what they believe to be friends. Hazuki is a fun and loyal girl who easily gets a bloody nose, especially when her emotions are unstable. Ayumi never breaks her cool character and Mio is a child prodigy who has some quirky hobbies. The trio gets caught up with a serial killer who seems to be hunting down students just like them. The only way the case makes sense is if the killer is also one of their classmates…