Relation to Zero is the seventy third chapter of the Vampire Knight manga.
Sara is shown testing the new blood tablets on one of her servants to which she states is delicious.
Yuki and Yori talk until Yuki becomes very hungry and she continuously thinks about how tempting Yori's blood is. She pins Yori down, warning her that she might assault her at some point but Yori only responds stating that Yuki is not scary.
Maria meets Zero as he lays on a bench and questions his ability to sense vampires unless they have killing/dangerous intentions and he retorts asking why a vampire would be out in the sunlight. Maria reveals that she's unable to find her way back and he leads her back to Cross Academy. Maria questions Zero's hatred towards vampires as he cannot hate them all otherwise he would have killed Yuki for "betraying" him. She also points out that Yuki gives out humanistic-vibes despite not being human. Zero ignores that point and says that he had never considered it (Yuki's awakening) as betrayal and Maria starts violently coughing and falls. Zero catches her and carries her bridal-style and Maria compares Zero and Ichiru's dialogue as he carried her back to rest.
She states that she has been looking for Ichiru and says that she has now 'found' him as she touches Zero's upper chest (showing that she can sense Ichiru's blood running through Zero's veins) and empathizes with him. As they finally reach Cross Academy, Yuki sees Zero escorting Maria back to her dorm and in retaliation, hides from him, although she is confused by this and questions why she's hiding from him.
A flashback shows Takuma hinting to Yuki that Sara has done something to the new Blood Tablets, most likely donating some of her blood to them as she seems to freely give it out but Sara interrupts them before he can say more.
In another scene, Sara slaps Takuma. She offers her blood to him, stating that he cannot resist, although he initially refused her.
Yuki (at the stairs) asks Zero for things between them to go back to the way it was in the past. In response to this, Zero states that she has become different and senses that she hasn't been drinking any blood for a long time(as she is only taking Blood Tablets) and leads her into the woods. He offers his blood from his wrist and Yuki denies wanting it. In response, he threatens to destroy the school and Yuki realizes that they cannot move forward without hurting each other. Yuki now not only accepts his blood but leans in to take it from his neck.