They share a secret.
When they were young, they had mentioned this secret casually, or confided it seriously to their parents, relatives, or close friends, but without exception, they did not take it seriously and just concluded the case as a "joke." Until, they met each other.
They smelled a familiar feeling on each other's bodies. From this secret——
Each of them has superpowers.
Purpose: To create a peaceful and unique girls' dormitory