Shirou runs a detective office. One day, Sakura visits his office. She is actually a younger sister of Shirou's old friend. "I would like you to find my older brother..."
There is a cafe near his office called Cafe Seaside, it is located in an isolated place. A rumor about the cafe spreads through the internet and people start gathering the cafe, 12 boys and girls. The master of the cafe in mask tells them about his plan, then they get on a ship and arrive on a small island. But what for? Various mysterious cases., endless serial killing, who is the culprit...?
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