In the bustling and futuristic city of Heartland, a young boy named Yuuma Tsukumo has a dream that everyone his age wants to achieve—earning the title of the greatest duelist! Sadly, due to his lackluster dueling skills, this dream is far from achievable. But when the school bully, Ryouga "Shark" Kamishiro, splits the key given to him by his father into two pieces, he inadvertently sets Yuuma on a collision course wi...