Kinkaku & Ginkaku

Kinkaku & Ginkaku (金閣 & 銀閣) are two youkai children who have an unfortunate run-in with the Sanzo Ikkou. Ginkaku had already died prior to their encounter. The two of them were closely associated with the arc villain, Kami-sama.

Kinkaku
Kinkaku has a warped sense of good and evil, and sees the world in black and white. This was brought about by the influence of Kami-sama who was twisted and childish himself, and saw the twins only as his pawns. Being as young and innocent as he is, Kinkaku is easily impressionable. He takes things as he sees them, as seen when he took to idolizing Gojyo who became "good" in his eyes by saving him from some street thugs.

Ginkaku
Ginkaku initially appeared to the Sanzo party as a huge mindless demon. At the time they did not know that the demon was only a shell, and not truly Ginkaku, whose soul was trapped in the gourd. Not much is known about Ginkaku's personality, except that he cares for his twin brother, as seen when he told Hakkai and Goku to stop Kinkaku.

Backstory
Prior to the Minus wave, Kinkaku and Ginkaku lived fairly normal lives with their family. But when the Minus wave struck, their parents and most of the other youkai in their village lost themselves and went berserk. Like in most cases, it seems that young youkai children--or undeveloped yoyukai as Hakkai put it--are not affected by the wave.

Scared, the two of them ran away to the forest where they got lost. Not long after, they were overcome with fatigue, and were too tired and hungry to continue on. Eventually they were found by someone who would evenutally be known as Kami-sama. Kami-sama took the two youkai boys back to his castle where he fed them, took care of them, and gave them whatever they desired.

At some point Ginkaku, the younger of the two, began to fear Kami-sama and lost faith in him. He tried to convince his brother that they needed to escape, but Kami-sama over heard their discussion. He claimed that Ginkaku was a "bad boy" and suddenly turned him into a ferocious and disfigured monster. Kami-sama claimed that it was because Ginkaku was being a bad child that he transformed. Kinkaku begged Kami-sama to help him turn his brother back and Kami-sama said if he did good things he could return his brother back to his original form. When Kinkaku asked what these "good things" were, Kami-sama said that he should kill all the bad people. Kami-sama gave Kinkaku special tool, a soul-stealing gourd, and sent the child on his way.

In a village near the forest, people started dying. According to the owner of the inn that the Sanzo Ikkou stayed at, the people that died were "people that you'd want to stay away from". What was strange about these deaths was that there was no trace of injuries. The victims looked peaceful, as if they had just lain down to take a nap. Unbeknownst to them, it was Kinkaku's handiwork, using the gourd to take away the souls of the "bad people."

Make a Wish
The Sanzo party arrived in town, and were forced to stay a while due to Hakuryuu 's illness. Gojyo, while being forced to run errands for the group, ran into some thugs picking on a kid. After saving the child, the two of them talked for awhile. Gojyo let off some steam, ranting to the child and talking about how his companions were all a "pain in the ass". The boy was non-other Kinkaku, wearing a limiter, and he asked if Gojyo's teammates were bad people. Gojyo said that they weren't, but then again they couldn't really be called "good people" either. Kinkaku stood up, smiling, and said that he would get rid of the "bad people" for Gojyo--"Kami-sama (God) is on his side"--and then left.

Upon leaving Gojyo, he attacked the remaining members of the Sanzo party in their room. He drained Hakkai and Goku's souls using the gourd. Sanzo barely managed to escape the same fate. When Gojyo returned to the room, he found it trashed, and his companions appeared to all be dead. Kinkaku appeared, expecting praise for his good deeds. Instead, Gojyo is angry and demanded the Kinkaku tell him what he did. Kinkaku was confused with Gojyo's anger and even more confused when Sanzo started moving. Sanzo shot at the monster Ginkaku and Kinkaku rushed to his brother's aid. The two of them disappeared, reappearing in the forest outside of town. Sanzo and Gojyo searched for them in the forest, and upon finding them, were attacked by Kinkaku.

Meanwhile, Hakkai and Goku, who were trapped in the alternate dimension of the gourd, crossed paths with Ginkaku who had actually been trapped in the gourd like them for over a year. Ginkaku attempted to fill them in while his brother continued to fight Gojyo and Sanzo outside.

Sanzo's words started to make Kinkaku doubt his faith in Kami-sama. Gojyo managed to shoot the gourd with Sanzo's gun and it shattered. Kinkaku was beside himself, unable to think of anything besides how angry Kami-sama would be. While Gojyo tried to talk him down, the Ginkaku beast began to attack them. Kinkaku tries to defend the monster--his brother. Gojyo calms him down--he'd been seeing a lot of his younger self in him--but when Kinkaku goes to talk to the Ginkaku beast again, it attacked him without any sign of remorse.

It is at that moment that the two remaining members of the Ikkou appeared and helped to stop the beast. Afterwards, Hakkai revealed the truth about Ginkaku. When Kinkaku thought that Ginkaku had been "transformed," Kami-sama had actually cast an illusion and made Kinkaku think that his brother had turned into a monster. In reality, Ginkaku's soul had been trapped in the gourd like Hakkai and Goku. But unlike them, whose bodies were still fresh and whole, Ginkaku's body was now a mummified corpse from being uninhabited for so long, and was simply rotting amongst the toys at Kami-sama's castle. Kinkaku couldn't bring himself to believe that his brother was truly dead, but before he had time to accept it, he was killed by Kami-sama and his prayer beads.

Trivia

 * The story of Kinkaku and Ginkaku is similar to Hansel and Gretel, the Grimm Brothers fairy tale Hakkai likened Kinkaku and Ginkaku to. It is a tale about a brother and sister who, abandoned by their parents, find a candy house while wandering the forest. However, the witch who lived there tried to fatten them up with candy and eat them. In the end, the younger sister traps the witch in her oven and bakes her to death, but Kazuya Minekura gave Kinkaku and Ginkaku a different ending. It is surprising that Goku knew this story.
 * Both twins are likely based on two characters from the Chinese classic "Journey to the West". In this story, Kinkaku and Ginkaku are two demon king brothers, known as the Great King Kinkaku (金角大王, Kinkaku-daiō) and the Great King Ginkaku (銀角大王, Ginkaku-daiō). The siblings possess five treasured tools; one of which, called the Crimson Gourd (紅葫蘆, Benihisago), had the ability to suck in their opponents, before melting them once they were trapped within.