Kekkaishi - Season 1 Episode 12 Demon Dog Madarao's Sealing

After a long battle, Madarao is weakened and begins to accept death believing that Kouya will die as well but Kouya gains even more power from Karasumori. Just as Madarao is about to give up, Yoshimori steps in and tells Madarao that his master is not allowing him to die and thus Madarao stands up. The two work together and strike Kouya down. The dying Kouya tells Madarao to kill him but Madarao can't because he has no power left, but Kouya refuses to die at the hands of a human and so Karasumori lends its power to Madarao, finishing off Kouya. But before the group can celebrate, Madarao's true ayakashi nature reveals itself and starts attacking Yoshimori. But Yoshimori, with the help of Hakubi and Tokine, successfully seals Madarao once again through much difficulty.