Lunar Legend Tsukihime - Season 1 Episode 11 Night of Disaster

Arcueid flees, and Ciel explains that Arcueid was the White Princess of the True Ancestors until Roa offered her a rose with blood that caused her to undergo a cycle where she would awaken for brief periods to kill Roa and then go to sleep once more. Shiki goes to follow Arcueid but comes upon Roa and Akiha. Roa begins to overwhelm the two until Ciel arrives, but she is dispatched. Roa retreats and Ciel regenerates her wound. At home, Shiki finds that he was adopted, and that he swapped places with the actual Shiki Tohno after he went berserk. Shiki then goes to Arcueid, and makes love to her in her apartment. When he awakens, he finds a note with the words "Bye, Bye" on them.