Gozu and Mezu

Gozu (left) and Mezu (right) are giant statues that guard the entrance to the afterlife. They faithfully protect this barrier to ensure that it is never opened and that no living being passes through it alive. They appear in episode 145.

Inuyasha & Hakudoshi
When Hakudoshi begins looking for the pathway between this world and the next, he learns of the Gate to the afterlife in the land of fire. However, he also learns that all those who appear before the guards of the gate turn into stone. He sends Kagura to InuYasha in order to tell him about the gate, hoping to use him as a guinea-pig and see if he turns to stone.

The entrance to the Gate is littered with the bones of countless demons, as well as their body parts that have turned to stone. When InuYasha and the others reach the entrance, a voice asks. "Do you wish to pass?" InuYasha responds yes, and Gozu and Mezu come to life. To InuYasha's surprise, the Windscar has no effect on the guardians, as they explain that they cannot be cut by a blade of this world, and that only the dead can pass. Miroku uses his kazaana on Gozu and Mezu as well, and it also has no effect on the pair of living statues.

InuYasha decides that even if he can't beat the guards, he can still force the gateway open. He cuts the chain that keeps the doorway locked and uses the Red Tetsusaiga to force open the doorway. Suddenly, an army of demons, led by Kagura, fly into the cave toward the now open gateway, hoping to get to the jewel shard before him, when they become bathed in a strange light. All of the demons begin to turn to stone, and Kagura jumps off her feather just in time to avoid becoming a permanent fixture of the cave.

During the brief moments that the gateway is open, Kagome declares that she senses the sacred jewel shard within it, making it no longer questionable that the last shard is indeed in the border of the afterlife.

Sesshomaru and the Tenseiga
Much later, When Tekkei's head is severed creating a river of blood, Naraku, along with Inuyasha and friends travel to the afterlife, Sesshomaru smells the river of blood, and Kagura tells him the pathway has already opened and closed. She informs him of another pathway, one that even he might not survive, refering to the gateway in the realm of fire. When confronted with Gozu and Mezu, Sesshomaru seems mildly amused by them, and when they declare they cannot be cut by a blade of this world, Sesshomaru unsheaths his Tenseiga, and the statues kneel to him in respect. The Tenseiga has the power to recall and revive dead souls, and being guards of the underworld, they would not oppose anyone who weilds the power of life and death itself.