In the town of Saima, when summer is about to begin, a group of six high school students intend to live a secret adventure by spending seven carefree days in a ruined mining facility.

On the island of Crete, a day-dreamy boy named Icarus befriends a mysterious creature with the body of a man and the head of a bull named Asterion (aka the Minotaur). When the King asks Icarus’ father, a famous inventor, to work on a secret project, Icarus realizes his new friend is in danger.