Tachibana Family
The Tachibana family of Minakami Village, which is a smaller branch of the Kurosawa family. Not a whole lot is known about the Tachibana family, save for the three children of the current generation. The Tachibana family must have played an important role, since their family house is one of the Twin Houses.
Unknown Father --- Unknown Mother
|
+-----------------------------+-------------------+
Mutsuki Tachibana(CS) Itsuki Tachibana(R) Chitose Tachibana
- CS - Crimson Sacrifice
- R - Remaining

Itsuki (立花 樹月) and Mutsuki (立花 睦月)
Itsuki and Mutsuki Tachibana were 15-year-old twins, who were next in line to perform the Crimson Sacrifice Ritual. They did not want to participate in the ritual, as they were very close, but could not run away as Mutsuki was too weak. Their good friends Yae and Sae Kurosawa were next in line to perform the ritual, and Itsuki and Mutsuki made a pact that, if their ritual was to fail, Itsuki would not let the same fate befall the Kurosawa twins.
Itsuki and Mutsuki completed their Ritual; however, it failed and Mutsuki did not become a butterfly, and subsequently the Hellish Abyss was not appeased. Itsuki and his sister Chitose were left alone in the house. One year later, when it was time for the Kurosawa twins' ritual to take place, Itsuki sent a letter to his childhood friend, Ryozo Munakata, informing him of the plan he had made to help Yae and Sae escape the village.
As the day of the ritual drew closer, Itsuki enacted their plan, writing in his diary that it may be the last task he ever performed. He distracted the villagers while Yae and Sae escaped into the forest. For doing so, he was locked in the Storehouse. He then hanged himself, unaware that Sae had been recaptured.

Chitose (立花 千歲)
Chitose was the younger sister of Itsuki and Mutsuki. She had poor vision, so was given a bell by Itsuki so he would know whenever she went near a dangerous place. She knew nothing of the rituals being performed in the village, or that her brothers were next to perform it. She expressed her confusion during the aftermath of the ritual in her diary.
Near the time of Sae and Yae's Ritual, Itsuki gave Chitose the key to his room, to give to Ryozo Munakata when he came to the house. However, when Ryozo arrived Chitose became frightened and hid, never giving him the key. She blamed Yae for her brother's disappearance, after the Kurosawa twins' escape from the village and Itsuki's subsequent detention in the Jailhouse. Chitose was left all alone in the house, saying she could feel a "presence" and that everything, inside and outside, was dark. She became stuck in the closet and later died there- whether she starved or was taken by the Darkness is unknown.