Tsukihi stays at home during the majority of summer vacation. At home, she has to deal with the suspicious activities of her older siblings, and her violent fit was, fortunately, evaded by the two.[2] She is soon left alone at home after Koyomi and Karen head to the Kanbaru Residence to meet Suruga. Upon Koyomi's return, however, two mysterious guests head to the Araragi Residence: the onmyouji-shikigami teamup of Yozuru Kagenui and Yotsugi Ononoki. Without any idea of what is in store for her, Tsukihi answers the door, only to be overwhelmed by Yotsugi's Unlimited Rulebook. The powerful attack completely destroy's Tsukihi's upper half, causing Koyomi to lose himself in a fit of rage, although Yozuru was able to disarm him before he could hurt anyone. It was there that Yozuru reveals that Tsukihi is a "fake" sister and is an immortal oddity called the phoenix. Due to her nature as an oddity, Tsukihi quickly recovers from Yotsugi's attack; meanwhile, Yozuru and Yotsugi decide to leave after Shinobu asks for the two to retreat for the meantime.[1]
As Tsukihi rests at home, Shinobu decides to explain the truth behind Tsukihi's existence, pointing out that Tsukihi is actually not a phoenix, but a supernatural cuckoo called the "Dying Bird", who reincarnates itself as a child in the womb of a chosen mother, which in this case is Koyomi's mother. Soon, Tsukihi wakes up, only to be shocked upon discovering that Koyomi stole her first kiss, and they had a short talk about their current relationship as siblings. This talk would give Koyomi the drive he needs to take on Yozuru and Yotsugi.[3]