The episode opens with Zero who is coughing over the bathroom sink because of his blood tablets. Memories of the vampire that attacked his family haunts him. Then, the scene turns to Kaname who thinks to himself that it will only be a matter of time.The Day Class students are discussing who they are giving chocolates to for Valentine's Day which happened to be fast approaching. The representative complains about this, but thinks of Ruka and decides he will join the celebration, too. The guys can't help but get jealous because the girls all prefer the students of the Night. Yori tells Yuki she doesn't plan on giving out chocolates to anyone, but Yuki is thinking about making chocolates for Kaname. Zero has no intentions of joining in this celebration.
Headmaster Cross lectures Zero and Yuki about their upcoming duties involving Valentine's Day, though Zero believes the event should be cancelled. The Headmaster believes that by allowing the students to give out chocolates to the students of the Night, it is helping humans and vampires to come closer to being able to co-exist. Yuki breaks the tension between Zero and the Headmaster by handing out Valentine's coupons, then she drags Zero out of the room.
Yuki is disappointed that the Headmaster directly says things that hurt Zero right in front of him. In a flashback, Yuki remembers the first time she saw Zero when Headmaster Cross took him in. His family had just been killed by a vampire, and he needed to be cleaned up. He didn't speak a word, but Yuki still cleaned up the blood that was covering him. Surprisingly, he wasn't hurt.Because it's the day before Valentine's Day, the girls of the Day are all excited and try to hand out chocolates early. Zero turns down everyone who tries to hand him some. Back in the Moon Dormitory, the students of the Night Class can hear all the screaming from outside. Aido wants to make a bet with Akatsuki about who will get the most chocolates. Shiki believes this is just troublesome. Kaname arrives, and the students of the Night Class prepare to leave their dorms. Yuki tries to stop the students of the Day Class from trying to hand out chocolates to the Night, but some of the girls refuse to give up. After trying to go over the wall around the dorms, one of the girls falls only to be caught by Zero. Zero finally decides to threaten to stop the next day's events. At this time, the doors open to allow the Night Class students to exit causing the Day Class students to scream in excitement and push Yuki out of the way. As the Night students walk by, they stop to stare at Zero, and Kaname asks how he is feeling and tells him to take care of himself. This makes Zero mad and causes him to threaten Kaname. Yuki has no clue as to what is going on.
Yuki decides to make chocolates that night while thinking about Kaname. Zero watches, but then heads off on his own only to suffer from an attack. Headmaster Cross approaches him with blood tablets, but Zero refuses them. Yuki awakens after sleeping during school. She tells Yori that her hand-made chocolates didn't turn out all that well, so she just bought some instead. Zero criticizes Yuki, but it is time for them to return to their job as prefect. On the way, Yuki is bothered by what is going on between Zero and Kaname, but shakes it off. The Night Class students exit their dorms to find the Day Class students lined up at gates eager to hand out their chocolates. Each Night student has a gate with their name on it for them to go to and recieve the chocolates and confessions from the Day Class students. Aido tries to approach his gate before he is told to, but is stopped by Kaname. The events begins. After being disappointed she isn't getting any chocolates, Ruka receives chocolates from the representative and resents saying this. Everything goes well except Aido asks one girl what her blood type is, but Yuki catches this. Kaname only accepts a few chocolates and then decides that his hands are too full.
Yuki misses her chance to give her chocolates to Kaname, but the chocolates fly out of her hands when some of the Day Class students run into her. Zero picks them up and throws them to Kaname only to have Yuki yell at him for that. Zero is hit by the sudden urge to drink blood after seeing Yuki's neck, but resists it. Kaname hands all of the chocolates he received to Seiren except the one from Yuki. Yuki looks for Zero only to realize everyone is gone.At the horse stables, the student Zero saved from the fall earlier approaches him to hand him chocolates, but Zero is suffering from the urge to drink blood and tells her to go away. Later that night, Yuki is having trouble finding Zero. During the Night lessons, Kaname notices that all but two of the Night Class students, Ichijo and Seiren are missing. The scene switches to Zero who is still suffering from his attack. The missing Night students approach him and try to pick a fight. Akatsuki tries to stop this, but is knocked to the ground. Zero challenges them, and Idou freezes the ground beneath them. Akatsuki produces fire, but Yuki appears and tries to break up the fight before it starts. The Night students give up and head back to their lessons. Zero refuses to answer Yuki's questions.
Zero once again is in the bathroom suffering. Yuki stands on a small bridge and tries to figure Zero out. She goes looking for him only to find him sitting against a wall in a room. She places the only chocolate she made that turned out correctly in his mouth, but Zero still does not speak. Zero almost gives into his urge to drink Yuki's blood, but stops himself and leaves the room. Yuki finds a blood tablet on the floor, wonders why it is there but doesn't make the connection with Zero. The Night Class students apologize to Kaname who forgives them. The episode ends with Zero trying to take blood tablets.