WARNING: The following contains major spoilers for Season 1 of Yashahime: Princess Half-Demon, now streaming on Funimation and Toonami.
As Yashahime heroines Towa, Setsuna and Moroha magically pass between modern Tokyo and Feudal Era Japan, they take on many devious demons who channel power from the rainbow pearls. However, the fierce young warriors also encounter inexplicable magical entities that complicate their lives in intricate ways. One of these entities is the mysterious Dream Butterfly.
The one most affected by the Dream Butterfly is Setsuna, the estranged daughter of Sesshōmaru and Rin. When Setsuna was little, the Dream Butterfly cursed her, making it impossible for her to sleep or dream. With such remarkable power and omnipresent symbolism, the pink and purple butterfly is a central issue in Yashahime: Princess Half-Demon. Let’s unravel the mystery of the Dream Butterfly and how its curse has impacted Setsuna.
The Dream Butterfly, or Yume no Kochō, is an enigmatic entity that can pass between the dream world and real world through the Tree of Ages. It’s unknown whether the Dream Butterfly is a spirit itself or simply has a strong connection to spirits, but its ability to navigate both worlds alludes to its spiritual significance. In the second opening of Yashahime Season 1, multiple Dream Butterflies are seen circulating the Tree of Ages, so there are potentially many more than what's seen in the series proper.
Beyond its ability to cross dimensions, the Dream Butterfly has the unique ability to curse victims by “eating their dreams and memories.” Though it's unknown how, the butterfly cursed a young Setsuna and made it impossible for her to sleep at all. The “dream-eating” curse not only causes insomnia but also memory loss. It's implied that the butterfly’s magic is directly connected to the erasure of Setsuna's early childhood memories with her sister Towa.
While Setsuna initially has little understanding of her insomnia, her monster-hunting cousin Moroha provides some insight into the curse. Moroha explains how the butterfly escaped the dream world to put its sleep and dream-eating curse on her. Ironically, Setsuna has the ability “Moon of the Resting Moth,” which produces a powder that puts her targets to sleep. Moroha also prods Setsuna about trying the ability on herself, which she confirms doesn’t cure her condition.
Haunted by the past, Towa feels responsible for Setsuna being cursed after letting go of her hand during a forest fire – her last memory of her sister before falling through the Spirit Tree portal. Setsuna, on the other hand, has no recollection of Towa whatsoever due to the Dream Butterfly, only deepening Towa’s regret. The half-demon heroines have many objectives throughout Yashahime Season 1, but Towa’s main priority is finding the Dream Butterfly to end its curse on her beloved sister, allowing her to get some much-needed rest and hopefully recover her childhood memories. The butterfly, however, is nearly untrackable, but Towa does manage to spot it in her dreams before failing to catch it.
The Dream Butterfly’s curse may be agonizing for Towa and “annoying,” as Moroha calls it, but it also comes with some perks for Setsuna. In Yashahime, Episode 8, the half-demon trio is attacked by an owl demon who shoots out sleep rays to infiltrate their dreams and discover their weaknesses. Setsuna, however, evades such attacks due to her inability to sleep or dream.
Moreover, Setsuna doesn’t experience the loss of her demonic power during the new moon like her sister Towa. Moroha theorizes that the Dream Butterfly’s dream-eating must have a connection to the power of the moon as well, nullifying the magical drawbacks of its absence. Moroha’s analysis isn't exactly thorough, though, so it’ll be interesting to learn more about the Dream Butterfly’s connection to the moon.
Another confounding element of its power is its connection to Rin, Towa and Setsuna's mother who’s been put into an eternal slumber. The Dream Butterfly is shown circling Rin as she sleeps, implying that it may also have the power to inflict neverending slumber on its victim. The Spirit of the Tree of Ages made a pact with Sesshomaru that put Rin in eternal stasis inside the tree to protect her from Kirinmaru, which could rely on the Dream Butterfly’s magic.
In the finale of Yashahime Season 1, Setsuna is slain by Kirinmaru in battle and her sleepiness returns, the Dream Butterfly landing on her head. As the curse ebbs, her last words to Towa are “Goodnight sis.” To find out whether Setsuna survived and her memories returned, fans will have to wait to learn more about the Dream Butterfly’s curse in the confirmed second season: Yashahime: Princess Half-Demon: The Second Act.