Post-DSoD. Kaiba's experiment with the space elevator fails. He can't access the afterlife, and wakes up in a hospital, disappointed. He is wrong, however. The experiment succeeded, just not in the way he hoped... He was able to open a portal to the afterlife; it's just that he wasn't able to get in. Something, however, managed to get out...

After the tumultuous events of the Tournament of Shadows, Yugi and his friends must join forces with the Demon Lords to prevent an ancient evil from destroying all existence. Victory is almost impossible, failure is unacceptable. Apocalypse has come.