There exists a legend about a king who obtained a relic from a lost civilization and used its power to grant any wish to unite the world. This relic, ‘Sora no Ison’ (Legacy of the Sky), was sealed afterwards by the ‘holy keys’ somewhere in the world. Countless persons have attempted to find it, but none of them could even find a trace of its location.
Haruto is a hopeless guy who was forced by the headmaster Spiano to attend the Academy, but ended up skipping all classes. When she made him work part-time, an unfortunate incident caused him to carry a huge debt to her. To pay off the debt, he was unwillingly tasked to explore to the depths of a sealed ruins as part of a supplementary test. His fellow test-taker Akina mentioned that it was rumoured that the elusive relic was sealed deep in the ruins. Vowing to become rich and to show Spiano up, he faced the challenge with heightened vigor.