The protagonist (name can be changed) is a highschool student in his first year. He and his classmate childhood friend, Hayami Arisa, participate together in the maiden voyage of the luxury cruiser "Dynasty".

The passengers are celebrating on top of the Dynasty's deck. However, a mysterious explosion crashes the party and causes the boat to sink. Though the protagonist hastily boards a lifeboat to escape from the danger zone, their group of boats soon loses sight of the others in front and they become adrift.

Before long, the separated group manages to take shelter on another cruiser called "Pandora" that suddenly appeared before them... Unfortunately, this mysterious ship becomes the site of multiple murder cases where the survivors are killed off one after the other.

Can the protagonist solve the case? And can he protect Arisa from harm?

Expose the trick behind the locked-room murder cases and nail down the culprit!

[Translated from the Official website]