Casts:

EXO M: Six students who’s missing.

EXO K : Six students at 3^rd grade.

YoonA: 32 years old. One of teacher. She worked as a teacher in the school after he finished his college. Beautiful and kind.

Yuri      : 30 years old. YoonA’s bestfriend. She was her junior at high school in the same school.

Taeyeon : 35 years old. Beautiful and smart. Kim Jongdae EXO M’s noona. Until now, she still try to expose Jongdae’s lost.

Sulli      : 30 years old. Beautiful, cute and smart. Kim Minseok EXO M’s yeodongsaeng. She still miss Kim Minseok and never stop to hope that he’ll back someday.

SHINee : One of school group that being investigated 15 years ago.

Krystal : EXO K’s classmates. A little bit annoying but smart. She knew everything about the school history.