Switch Witch

Switch Witch (スイッチウィッチ) is a manga written and illustrated by Akita Shoten. The manga has been serialized in Young Champion since February 25, 2014.

Plot
Switch Witch centers on a girl named Wakaba Himekawa, who is aware that she is growing up slower than other people, but otherwise lives a peaceful life. On the same day that she finally gets her first period, her childhood friend Takaya confesses that he loves her. While Wakaba had never felt that way for her friend before, she is still happy, if confused. As she is about to answer Takaya's confession, an alarm suddenly sounds, and a broadcast begins that will change her everyday life.