Mount Musubi

 is a mysterious mountain that plays a major role in Hanyō no Yashahime. It is the objective for Towa Higurashi's quest to search for the Dream Butterfly to reclaim her twin sister's dreams and memories.

History
600 years ago, after Rion was killed, her soul has been trapped in this astral body and sealed in Mount Musubi. Eventually, Kirinmaru used the Dream Butterfly and forced her to meet him in dreams.

Season One
Sometime after returning to the Feudal Era, Towa asked Kohaku for information regarding the whereabouts of the Dream Butterfly. The new chief of the demon slayers searched through some texts indicating them inhabiting the mysterious mountain that resides in the east.

Several days later, Towa attempts to search for the mountain on her own after Setsuna had left earlier that morning. Unfortunately she ends up lost whilst encountering a mysterious man.

Towa later attempts to search for the mountain again, this time accompanied by Setsuna and Kirara. Unfortunately, she only finds Mount Omusubi, a mountain that resembled an onigiri rice-ball, but even though the old farmer has never heard of the name of Musubi before.

Season Two
Many weeks later since the resurrection of Setsuna, the location of said spiritual mountain is revealed just outside Bokusenō's forest. They learn from the ancient tree that the Kyūyōkon Root can be located in a Demon Spirit Tree at the mountain. Towa and Moroha approach it, but are warned by Setsuna that it is cloaked by a strong demonic barrier, which was precisely why Towa could never find it before. From within the center of the center, lies a deeply sleeping fawn-eared, raspberry-haired girl on a swing or scale that emanates a pale greenish glow holds of a tree.

Towa, and Setsuna didn't get pass through the barrier except for Moroha. Later, Rion tells her that she is immune to the barrier. Moroha attempts to let them in. One of the voices they hear is from Kirinmaru, annoyed that Moroha got through it so easily. Rather than risk a battle from the Half-Demon Princesses and friction from Rion, he puts them to a test that they easily passed. He did not interfere when she gave them a Kyūyōkon Root. Rion have continued to befriend the Half-Demon Princesses and want to slay her own father the Lord of the Eastern Lands. Rion tells them that she was dead 600 years ago that her father did not accept her death. Also Rion warns them of the Degenerate Age since Kirinmaru traveled every corner of the world except, beyond space and time which means the future that Towa was living.

Kirinmaru is after the spirit named Akuru and capture him so he can move the Windmill of Time until it will cease to exist that they were surprised as what the Spirit of the Tree of Ages said. Towa hugs her in pain that she's all alone, Rion was surprised and said that she's a kindhearted person. Towa plays the Hoshikiri no Fue and it turns the new weapon: the Zanseiken, she uses the Sōtō no Sōryūha to defeat the Demon Spirit Beasts. After that, they leave the mountain with Rion, as they start heading back to Kaede's village, Sesshōmaru and Jaken have arrived.

Trivia

 * Its name may be inspired by.
 * Mount Musubi shares similarities with Mount Hakurei;
 * Both had a mysterious barrier surrounding it.
 * Both were used to conceal an important character; Naraku and Rion.
 * Both had an important role in their respective stories; In the original series, Naraku used it to hide away in order to discard his human heart. In the sequel, Towa sought the mountain out to find the Dream Butterfly that cursed Setsuna.