Black Pearl

"Seeing, but never seen; protected, yet unknown to its protector: the Black Pearl."

- Sesshōmaru

is a demon relic in the InuYasha universe which provides its bearer with a gateway to "the other side".

Background and Purpose
Knowing that his elder son Sesshōmaru would actively seek the Tessaiga following his death, Inu no Taishō decided to keep the sword with his remains in the other world — where his firstborn could not follow — until Inuyasha was able to use it himself. In order to provide Inuyasha with access to the other world, and thus the sword, he commissioned the demon Hōsenki to create a jewel that could open a gateway there. Once forged, Inu no Taishō had Myōga hide the pearl within, or behind Inuyasha's right eye.

Some 200 years later, Sesshōmaru finally tracked down the pearl's location after decades of searching and claimed it forcibly from his youger brother's eye. He used it to open the portal to his father's resting place and passed through it, with Inuyasha, Myōga and Kagome following him. Once the sword was claimed, the characters returned to the world of the living through the same portal. After closing the way, the pearl returned to Inuyasha's eye and became a permanent part of him.

In the later seasons and chapters, the characters discovered that a jewel shard had somehow made its way to the netherworld. After asking how to use the pearl to reach the graveyard again, Tōtōsai and Myōga informed Inuyasha that by providing him access to his inheritance, the Pearl had served its function and could no longer link them to the netherworld.

Trivia

 * The Black Pearl looks much like a tainted Shikon no Tama.

黑珍珠 Kuroshinju