"Witches lurk among these girls."
It was supposed to be Ema's first day of high school. But instead of waking up in her bed, she found herself in a dark prison cell. She found herself suddenly trapped in an island prison, isolated in some unknown, distant sea. In her confusion, an owl informed Ema of her new situation:
"You have been identified as a potential witch — a threat to the world."
"Thus, you will live here as a prisoner for the rest of your life."
The life Ema had taken for granted had suddenly collapsed. As she began her new life as a prisoner, Ema got to know the other girls in her situation. Her fellow witch candidates.
However, one day, the owl gathered the prisoners for a shocking announcement:
"We will be holding a witch trial."
One by one, the girls would have to single out a witch among the thirteen of them... In other words, they would have to vote out the next candidate to be executed.
It was the beginning of a cruel game indeed...
