Yu-Gi-Oh!: The Dark Side of Dimensions

Six months after the end of the original manga, Yūgi Mutō and his friends are preparing to graduate from high school. Even though he's moving forward, Yūgi still struggles to come to terms that the Pharaoh is no longer with him at times. However, other people may not be so willing to let the past alone. After learning that his long time rival has gone to the afterlife without him claiming victory, Seto Kaiba desperately searches for a way to revive him by digging up the Millennium Puzzle from the Shrine of the Underworld. On the cusp of accomplishing this, his plans are foiled by mysterious stranger, Aigami, who holds power over dimensions.

Synopsis from Anime News Network