When Tsumugi and Hiiragi reach the Hie Shrine, they find that Shion, Tsumugi’s mother, is not there. Instead, Izuru, who’s been searching for Tsumugi all along, arrives and asks her to return to the Oni village because the Snow Gods have been acting strangely. Believing Shion is gone forever, Tsumugi is crushed and cuts ties with Hiiragi, which makes him suppress his feelings and turn into an Oni—demon-like creatures from Japanese folklore that are often misunderstood as purely evil but are actually more complex. When a Snow God detects Hiiragi’s transformation, it swallows him and takes him to the Hidden Village. There, Hiiragi manages to break free from the Snow God’s belly with the power of love, demonstrating that emotion and connection can overcome even supernatural forces. He’s brought before Gozen, the leader of the Oni, who explains that the Snow Gods were meant to guard the Oni, creating a barrier between their world and humans. However, over time, these gods have become hostile, attacking the Oni instead. The elders believe the Oni are being punished, and a key to their protection lies in the Spirit Mask, which controls the Snow Gods and allows the Oni to stay hidden. The mask is kept on Oni Island and must be worn by someone selfless willing to stay isolated forever to maintain the balance.
Tsumugi develops her own theory: if she destroys the Spirit Mask, the Snow Gods will leave the Oni, believing the gods are angry because the Oni try to control them. Gozen supports her idea, but warns that doing so will expose the Oni to the outside world. Unaware that Shion wears the mask and controls the Snow Gods, Tsumugi’s decision to destroy it triggers a chain of events. Shion, who has been controlling the gods from behind the scenes, is moved by her desire to reunite with her daughter and chooses to command the Snow Gods to bring the Oni into her realm instead of keeping the village hidden. She frees the Oni trapped on Oni Island, but the destruction of the mask causes a catastrophic avalanche, destroying the Oni realm and trapping Tsumugi within it. During this ordeal, Tsumugi experiences a moment of clarity, reflecting on her time with Hiiragi and even traveling back in time to the moment he decided to help her at the bus stop, suggesting that their bond has transcended usual boundaries. Hiiragi’s determination to reunite with Tsumugi allows him to break free from the Snow God’s captivity, and the two are eventually able to escape the collapsing realm, meeting again at the bus stop. Tsumugi explains that, since Hiiragi is no longer an Oni, he cannot access the Hidden Village anymore—only Oni can, now that the balance has been restored. This ending hints that the traditional isolation of the Oni is no longer necessary, as the oppressive barrier between the worlds has been lifted, and both can live freely and openly.
In essence, the story is about the importance of balance—between solitude and connection, tradition and change. Hiiragi, an introverted boy forced into isolation by societal expectations, and Tsumugi, an extrovert longing for adventure, embody contrasting ways of being. Their journey culminates in the realization that neither extreme—total solitude nor unbreakable closeness—is healthy. By choosing to end the Oni tradition of self-imposed isolation and fostering understanding and love, they create a new, more harmonious way for the Oni and humans to coexist. The ending signifies that true freedom comes from being true to oneself, embracing change, and finding the courage to challenge long-standing traditions for a better future.
