The Taira clan, also known as the Heike, holds immense authority over Japan. When a young girl, gifted with an odd eye that allows her to see the future, foolishly disrespects the clan, her father pays the price of her crime with his life. Soon after, as fate would have it, Taira no Shigemori—the eldest son of the clan leader—stumbles upon the same unfortunate girl, who now calls herself Biwa. Biwa informs him that the downfall of the Heike is imminent. After learning of the great injustice Biwa suffered at the Heike's hands, Shigemori vows to take her in and care for her rather than let her be killed. In an era of rising military tension, the Heike are in the midst of a cunning struggle for power, and bloodstained war is on the horizon. Shigemori, whose eyes allow him to see spirits of the dead, is both anxious and hopeful to prevent his clan's demise. Biwa, however, is reluctant to reveal the future to him and must adapt to her new life filled with both happiness and sorrow in this pivotal chapter in Japanese history.

Eight hundred years ago, terrifying demons threatened mankind's existence. On the brink of extinction, humans prayed to their gods, calling out for someone to save them. Emerging from these desperate pleas for salvation, battle deities known as the Idaten were born. Possessing unnatural strength and endurance, the Idaten managed to defeat the demons and an era of unprecedented peace was finally ushered in. Having never encountered demons before, the present generation of Idaten knows nothing of the demon's brutality, but they have instead only lived a peaceful existence. Training under Rin, the only remaining Idaten from 800 years ago, the new Idaten find ways to survive in a time where they have seemingly outlived their usefulness. However, when the tyrannical Zoble Empire resurrects a demon, the misfit crop of gods are called to the battlefield against their natural enemy once more.

Hellsing, an organization specializing in dealing with supernatural threats, is called in to eliminate a vampire that is turning the villagers of Cheddar into ghouls. To put an end to this, the leader of the organization, Sir Integra Fairbrook Wingates Hellsing, dispatches her most formidable asset: a powerful vampire known as Alucard. Armed with only a single handgun, Alucard wreaks havoc on the monsters plaguing Cheddar. However, a young police officer, Seras Victoria, gets caught up in the chaos and becomes mortally wounded as a result. Taking pity on the girl, Alucard gives her a choice: die as a human or live on as a vampire. Seras accepts his offer and begins a new life as a member of Hellsing. Though it was her decision, Seras struggles with the fact that she is no longer human. Nevertheless, she must embrace being a creature of the night soon if she wants to survive on the front lines in the fight between humans and the supernatural.

After preventing Japan's destruction, Akira Takizawa made one final request to become the King of Japan, before he erased his memories once again and disappeared. Leaving Saki Morimi with his cellphone, the only clue she has in regards to Akira's whereabouts is the message, I'll be waiting where our journey started. Six months later, rumors have spread about Akira, and Saki's search leads her to New York City. However, Saki is not the only person who goes to investigate—with several billion yen burning a hole in their pockets and a challenge to save Japan, the remaining Seleção are not far behind. Some are willing to help Akira achieve his goals, but a few are making dangerous moves in order to eliminate him and achieve their own picture of a better Japan. With rising stakes and new revelations, the game is still on.