Teenagers Who Won't Live Past the Age of 20

In a certain corner of the world, there is a group of children who have been living in a laboratory since the day they can remember. … In their perception, the laboratory is the "world", and people in white clothes doing various experiments on them every day is "life". … Some people say that they are destined not to live past twenty, but they have no idea how long they will live. … Until one day, the laboratory was destroyed, and the survivors escaped and saw the outside world for the first time...