Daybreak (東雲 Shinonome) is the prequel to the Kyoukai no Kanata anime series, bundled with the seventh Bluray/DVD volume and released on July 2, 2014.
Three years prior to the beginning of the series, Hiroomi Nase faces off in an abandoned warehouse with a human-like youmu who had just killed a girl. Suddenly, Hiroomi is trapped in spider silk and is about to be struck down by the youmu, but Izumi Nase arrives and saves him. The youmu transforms into a giant spider but the adept Izumi quickly disposes of it. Hiroomi laments his inablilty to subdue the youmu, but Izumi says that he will have more opportunities later and asks him to take an important task that concerns the entire Spirit World.
At the Nase manor, Izumi describes the task to Hiroomi, which involves defeating the immortal half-youmu, Akihito Kanbara. Mitsuki Nase is hiding outside the room where her siblings are gathered but Hiroomi sees through her Invisibility Cage as he leaves the room. Upon seeing Yakiimo on her shoulder, Hiroomi reminds Mitsuki that members of the Nase household are not allowed to keep youmu as pets. Mitsuki defends her familiar and responds by saying there are different kinds of youmu, implying that not all of them are bad. She then states that she wishes to accompany Hiroomi on his mission but he refuses, saying that he doesn't want his beloved baby sister to be involved. This irks Mitsuki and she calls him 'gross'.
Hiroomi boards a train which will take him to where Akihito resides. Suddenly, Mitsuki appears by his side, proud of the fact that this time, using her Invisibility Cage, she was undetected by her brother. He demands that she goes back but she refuses. After disembarking, the two leave the train station and Miroku Fujima steps out from his place of hiding. The siblings come upon Akihito's residence in the countryside. As Hiroomi runs ahead, something drops on Mitsuki's head. She looks up and briefly sees a woman dressed as a Spirit Warrior running through the trees. Mitsuki looks down and picks up capsule filled with cursed blood.
Hiroomi sneaks into Akihito's home and attacks him. Akihito escapes into the forest and is pursued by the two Nase siblings. Yakiimo discovers Akihito hiding in some bushes and the two siblings confront him. Akihito attempts to reason with them, but Hiroomi is obstinate and calls Akihito a youmu as an insult. Akihito, tired of this treatment he's received all his life, insists that he is half-human. To diffuse the situation, Mitsuki suggests that Akihito comes into the custody of the Nase Clan for protection from other Spirit Warriors. Back at his home, Akihito declines the offer but Hiroomi forcefully insists by snaring Akihito's neck with his scarf. The two struggle back and forth but are interrupted when Miroku attacks them. They flee into the forest again and Hiroomi sets up a cage for protection against Miroku's attacks as Akihito unties the scarf around his neck. In the turmoil of battle, Akihito is gravely wounded while protecting Hiroomi. Miroku halts his attack as Izumi arrives, and they battle. It turns out that the two of them were expecting each other and that Izumi specifically assigned Hiroomi the task of capturing Akihito so that she could fight Miroku. Miroku's presence confirms to Izumi that the youmu inside Akihito is Beyond the Boundary.
Meanwhile, Akihito's youmu side surfaces and he attacks. Hiroomi is overpowered and Akihito severely injures him, scarring his back. Ayaka Shindou and Ninomiya Shizuku arrive and attempt to hold off the youmu. Mitsuki uses a cage to deliver the blood capsule she received to Akihito. It reacts with him and Akihito reverts to his human form. Elsewhere, Miroku is locked in combat with Izumi. He notices the commotion of the other battle and the affect that the cursed blood had on Akihito. He then foretells his next meeting with Izumi before disappearing. Akihito wakes up with blood on his hands and is horrified at what he did to Hiroomi.
At the train station, Mitsuki informs Izumi about her receiving the cursed blood capsule, and Ayaka says that the cursed blood belongs to a clan of Spirit Warriors. Akihito asks Hiroomi to leave because those who get involved with him will meet misfortune. Hiroomi stubbornly says that he cannot leave Akihito alone. Hiroomi begins to understand that there are indeed different kinds of youmu and begins to accept both Akihito and Yakiimo. As daybreak arrives, Hiroomi states that he will become as strong as his older sister and protect Akihito. Tired of his current state, Akihito requests Hiroomi to kill him if Hiroomi ever obtains such power. Hiroomi then calls a truce between them and places his hands in Akihito's armpits, freaking him out.
In the post credits scene, Mirai Kuriyama receives a call from Izumi and then boards a train.