A class of 32 students receive a message from a mysterious sender called "King" at midnight, giving them a set of rules and an order.

Students:

Seat no. 1 - Zhang Yixing - Silent, minor character

Seat no. 2 - Kim Taeyeon - minor character

Seat no. 3 - Park Hyoyeon - minor character

Seat no. 4 - Choi Siwon - minor character

Seat no. 5 - Shin Changmin - minor character

Seat no. 6 - Krystal Jung - main character, gothic, cool, calm, suspicious, cold

Seat no. 7 - Lee Taemin - minor character

Seat no. 8 - Henry Lau - minor character

Seat no. 9 - Choi Jinri - supporting chatacter, easily panics, loud,

Seat no. 10 - Jung Yunho - supporting character, bad boy,

Seat no. 11 - Byun Baekhyun - minor character, quiet

Seat. no 12 - Kim Ryeowook - main character, class vice president, suspicious, responsible, studious, has a dark past

Seat no. 13 - Chen Kim - minor character

Seat no. 14 - Key Kim - minor character

Seat no. 15 - Kim Jonghyun - minor character

Seat no. 16 - Kwon Yuri - class president, responsible, studious,

Seat no. 17 - Onew Lee - minor character

Seat no. 18 - Lee Hyukjae - supporting character, jokester, byuntae, class clown, funny

Seat no. 19 - Park Chanyeol - minor character, nerdy, studious

Seat no. 20 - Im Yoona - minor character, girly, school princess, sossy

Seat no. 21 - Huang Zitao - supporting character, slow, kind

Seat. no 22 - Victoria Song - supporting character, intelligent, smartest in the class, studious

Seat no. 23 - Jessica Jung - minor character [not sisters with Krystal in this story]

Seat no. 24 - Choi Sooyoung - main character, smart,

Seat no. 25 - Tiffany Hwang - minor

Seat no. 26 - Sunny Lee - minor

Seat no. 27 - Oh Sehun - minor

Seat no. 28 - Seo Joonhyun - minor

Seat no 29 - Kai Kim - minor

Seat no. 30 - Lu Han - supporting, strong, school prince

Seat no. 31 - Xiumin Kim - minor

Seat no. 32 - Do Kyungsoo - minor

Teacher - Suho Kim