Ryou Bakura would probably never have even entered into the scene, were it not for an odd compulsion that drives him to seek out the Millennium Items. He's drawn to the Duelist Kingdom from the combined influence of Pegasus' Millennium Eye and Yugi's Millennium Puzzle.

The odd compulsion comes from the Millennium Item he himself carries: the Millennium Ring. In its inert state, it has the power to track the direction of other Millennium Items. But it also holds a darker power: the ability to trap souls in inanimate objects. Once long ago, a grave robber, attempting to obtain the Millennium Items, ended up with his soul trapped in the Millennium Ring itself. This shadow soul, Yami Bakura, emerges from the Ring whenever it is activated. Yami Bakura then takes over Ryou Bakura's body and continues his quest (even now) of getting the seven Millennium Items.

His quest takes him to Yugi and company, and he almost succeeds in sealing everyone's souls in their own cards, but the Millennium Puzzle fights back, drawing Yami Yugi out so he can fight for their freedom. Blocked as he was because the Millennium Puzzle gave Yugi a second soul, Yami Bakura then thinks of other ways to get ahead, including trying to switch his host from Ryou Bakura to Mokuba Kaiba, but Tristan manages to outwit Yami Bakura and set him back. Tristan thinks he threw the Millennium Ring away, but the Ring can be drawn back to its host at will. Learning of Pegasus's defeat, Bakura quickly switches gears to confront Pegasus, overpower him, and steal his Millennium Eye.

It is practically certain that the two shadow souls of Yami Bakura and Yami Yugi will cross paths again, since Bakura still wants Yugi's Millennium Puzzle.