The year is 2064, and Tokyo, where drawn "Giga" materialize, is in utter chaos. One night, Souma, who is at a loss because he cannot draw Giga, saying "Because I have no heart...", meets a kind-hearted girl named Ikaru. Encouraging him by saying, "There is no such thing as a person without a heart," she couldn't leave Souma alone, and the story of the two began. There is no such thing as a person without a heart. But, what if they weren't human――? "Gigajin," legendary beings that are drawn "Giga" yet possess a human heart. The journey of Souma and Ikaru, seeking a formless heart, will stir up a great storm in the world!! An art Battle Fantasy where hearts, pride, and everything else are at stake, grandly begins!!