Gegege no Kitarou (1968) EP36 - Diamond Youkai

A young girl named Junko enters a jewelry shop and wishes to have a large diamond appraised. The clerk laughs and says there's no way she found a diamond that large, but decides to humor her and have it appraised anyway. The appraiser (played by Salaryman Yamada) confirms to the clerk that it is a real diamond, but they decide to tell Junko otherwise and keep the diamond for themselves, not even telling their boss about it.

Kitarō later arrives at Junko's home, having received a request from her in the Yōkai Post. Junko and her mother tell him about how her father was studying diamonds from Jigoku Mountain when he suddenly disappeared in the middle of the night, leaving behind only the large diamond Junko found. Kitarō asks to see the diamond only to learn Junko left it at the jewelry store. That night, the two men from the jewelry store are awoken by the sound of evil laughter coming from the box they put the diamond in. When they inspect the diamond, they see inside it the face of Wanyūdō.

The next day, Nezumi-Otoko is feeding fish by Jigoku Mountain when he sees the two men. He pesters them and asks where they are going, and although they ignore him and shove him aside at first, they eventually tell him about they diamond supply they're looking for. Nezumi-Otoko runs to the GeGeGe House and asks Kitarō to come help him gather diamonds, but Kitarō is uninterested until he mentions they are at Jigoku Mountain. Medama-Oyaji believes they might have discovered an entrance to Jigoku, so they accompany Nezumi-Otoko to the mountain.

Inside the cave they find a giant man-shaped diamond. Nezumi-Otoko tries to grab it but Kitarō warns that his Yōkai Antennae is detecting yōkai energy from the area. Not one to be deterred, Nezumi-Otoko lays the diamond down and places a boulder on top of it, to save it for later. Further in they discover a Shinto temple like building, with diamonds scattered all over the ground. As Nezumi-Otoko tries to gather as many as he can, the two men walk out and claim all the diamonds as theirs. When the appraiser threatens Nezumi-Otoko with a switchblade, Kitarō fights him off with his chanchanko and warns the clerk about stealing the diamonds. Before Kitarō can convince him, however, Nezumi-Otoko strikes him on the back of the head with a diamond. He then suggests to the two men that they works together to collect all the diamonds and split them 50/50 once they get outside.

As they gather the diamonds and Medama-Oyaji tries to wake Kitarō, Wanyūdō makes his appearance and terrorizes everyone for trying to steal his diamonds. He fires a light ray from his mouth which turns the two men into diamonds, leading Medama-Oyaji to deduce that all the diamonds in the area are other humans and that Wanyūdō eats the diamonds. Wanyūdō chases down and eventually turns Nezumi-Otoko into diamond as well. Medama-Oyaji finally wakes Kitarō and informs him of the situation just as Wanyūdō fires his ray at them. Kitarō dodges but Medama-Oyaji is turned into diamonds. Kitarō's usual weapons aren't working on Wanyūdō, but he soon grabs a shard of a mirror and reflects the diamond ray back at him, turning Wanyūdō into diamond instead.

With everyone back to normal, Nezumi-Otoko and the two men prepare to resume gathering diamonds, but Kitarō scolds them and points out the diamonds aren't real. Sure enough, the diamonds soon begin changing back to human bones and skulls. They then hear a cry for help and find that the man-shaped diamond Nezumi-Otoko placed under a boulder earlier was actually Junko's father. The father and daughter are reunited and the jewelry store employees have learned their lesson. Nezumi-Otoko, however, has not learned a thing and chases after Junko asking for a reward for inadvertently finding her father.