It is attached to the railing at the 2nd floor of the Main Hall, New Building.
And in the Original, Another one is attached elsewhere. It is attached near the door to Rooftop at 3rd floor (Passageway part).
The official localized English transcript is not yet present. Please add it.
신관 중앙 홀 전등에 3층 옥상의 자물쇠 열쇠가 걸려있습니다. 열쇠를 갖고 장난치던 학생들의 소행으로 보입니다.