My Heart Keeps Beating Like a Hammer

While spending a day together, Satsu lets Buffy know that the number four represents death in Japan. Buffy has now had four vampires drink from her (The Master, Angelus, Dracula, and Spike), and Satsu fears that if she doesn't have one more vamp do so, Buffy will die. So Buffy is this then off on a mission to convince Angel to drink from her again, since Illyria bound his soul.