One night, a 2nd year college student was chatting with all of her friends from different nations. They have also created their own online personas. She reminded them to go out for a camping trip. They all came to meet each-other, spending times.

Suddenly, one of them found a big, deep, mysterious hole from the ground, causing them to follow. The other, pushed one. But they decided to fall down as well.

They all died, but revived as their online sonas. No one knows where they are until they saw a woman. Which she is actually their teacher, formerly for the ones who are older than any other college students' ages. She tells them to stay in a dormitory for a year. If any of them tries to leave, will die, one by one.