Natsuki Subaru is summoned to a parallel world on his way home from the convenience store. He's entranced at first by the fantasy world suddenly stretching before his eyes, but the cute girl he believes summoned him is nowhere to be found, and soon enough he's utterly lost. Then a gang of punks surrounds him, but he quickly learns that he doesn't have any of the powers that he thought all people transported to a parellel world should have. Just when he's about to be beaten senseless, a girl appears...

Emilia is hurriedly ushered to the capital along with the villagers under the orders of a mysterious benefactor while escorted by a rag-tag group of individuals from various and opposing factions. She has but one question on her mind: who could this man be and why would he go so far? Meanwhile, Subaru and Julius face off against the Archbishop of Sin Betelgeuse for the ultimate time. Unfortunately, he is very persistent even beyond death, belying his nature of Sloth. Subaru is relentlessly chased while he catches up to Emilia to save her one last time and answer her question.

Amid dying countless times, Subaru finally led the troops to victory against the White Whale and struck down the schemes of the Sin Archbishop of Sloth. After overcoming a painful ending to his these ordeals, he was reunited at last with his beloved Emilia… only to learn that Rem’s existence had been erased from the world, wiped out by the White Whale somewhere in the middle of his death loop. And now that the White Whale is defeated, Subaru and the others face a crisis no one could have expected.

The magic Roswaal is using to control the weather generates enough mana to attract the Great Rabbit, which draws closer to the Sanctuary in a massive horde. Emilia takes Roswaal and Ram to shelter in the graveyard with everyone else, but the Great Rabbit horde has already grown enough to engulf their surroundings. Just when all hope seems lost, Subaru and Beatrice appear before Emilia. So begins Subaru and Beatrice's first battle against the Great Rabbit, one of the Three Great Mabeasts.