On the Island of Yuyechu Middle School, a large group of seemingly ordinary yet mission-bearing students gathers. Wang Shun and others spent a wonderful week in an extremely comfortable environment, finally reaching Saturday's classroom. Facing these still children-like students, the three-dimensional image teacher suddenly announced an incredibly cruel fact—only through battle can one survive! Defeat means disappearance, while victory means continuing the nightmare-like infinite cycle. In times of crisis, can friends be trusted? Will apparent enemies speak the truth? All the excitement unfolds in 'Core Defense'!

孤岛上的御业中学，聚集了大批看似寻常却各负使命的学生。
王舜等人在无比舒适的环境里度过了美好的一周，终于来到周六的课堂。面对这群还是孩子的学生们，立体影像的老师突然宣布了一个无比残忍的事实——只有战斗才能生存！败即意味着消失，胜则要继续着噩梦般的无限循环。
在危机来临时刻，身边的朋友是否可信？看似敌人又是否会口吐真言？精彩尽在——《核心防卫》！！