Upon the creation of marble launching machines known as B-Daman, people started to participate in the competitive sport B-DaBattles. However, B-Daman contain hidden powers which enhance marble shooting that can be misused for combative purposes. One night, a certain object residing behind the walls of a restaurant calls upon Yamato Daiwa—a boy raised by cats. Yamato has been having visions of the object which resembles a machine familiar to everyone. Little does he know, hidden behind the walls is not a mere machine, but the fate of the world.

There is a strong guy, come and challenge Daikokuten Bell! Rumors were widespread in the world about the Bey Cemetery, The Gate of Makai. And the owner is Daikokuten Bell. He is the true Demon King who is proud of being undefeated at The Gate of Makai. Bell jacks the broadcasts around the world and declares war on all Bladers! The Devil's Bay in his hand, Dynamite Belial! In front of the unknown Beyblade, legends such as Valt Aoi also stand up to face him! Now, the legend of Demon King Bell, who has turned the whole world into an enemy, is about to begin! (Source: Official Site)

For centuries, the Iga and Kouga ninja clans have engaged in a bitter war. But when a ceasefire is ordered by the powerful warlord Ieyasu Tokugawa, the two clans are forced to put down their arms. Years later, Gennosuke Kouga, heir of the Kouga clan, and Oboro Iga, heir of the Iga clan, have fallen in love. Through marriage, both heirs aim to bring peace to the clans. But their hopes are dashed when flames of rivalry between their clans are reignited, and they are dragged into another war. Ieyasu's two grandsons have both claimed to be the next heir to the shogunate. To resolve this dispute, both the Kouga and Iga are ordered to send their 10 best warriors to fight in a bloody battle royale, with each clan representing one of the potential shogunate heirs. Two scrolls with the names of the fighters are given and are to be marked in blood upon the given fighter's death. The prize for winning is the favor of the Tokugawa shogunate for a thousand years. Torn between their love for each other and duty to their clans, Gennosuke and Oboro must ultimately decide the fate of their clans.

In the Kingdom of Midland, a mercenary named Guts wanders the land, preferring a life of conflict over a life of peace. Despite the odds never being in his favor, he is an unstoppable force that overcomes every opponent, wielding a massive sword larger than himself. One day, Griffith, the mysterious leader of the mercenary group Band of the Hawk, witnesses the warrior's battle prowess and invites the wandering swordsman to join his squadron. Rejecting the offer, Guts challenges Griffith to a duel—and, much to the former's surprise, is subsequently defeated and forced to join. Now, Guts must fight alongside Griffith and his crew to help Midland defeat the Empire of Chuder. However, Griffith seems to harbor ulterior motives, desiring something much larger than just settling the war...