High school senior Koyomi Araragi discovers a shocking secret one day after helping his classmate Hitagi Senjougahara—a secret he is never to tell.

Araragi leaves Kanbaru's house and meets a dangerous man named Kaiki. While following him, he runs into Senjougahara, who berates him for skipping his studies.

While taking Karen to meet Kanbaru, Araragi is put into a compromising position. On the way, he runs into someone asking about familiar things.

A recap episode retelling the events of Bakemonogatari from "Hitagi Crab" to Nadeko Snake", narrated by Koyomi. One day, Koyomi Araragi caught the body of his classmate Hitagi Senjyogahara, who was falling down after slipping on the stairs, knowing that it was dangerous to do so. However, her body was surprisingly light, as if the concept of weight did not exist.

A recap episode retalling the events of Bakemonogatari's Tsubasa Cat and the entirety of Nisemonogatari, narrated by Koyomi. During the summer vacation after all the apparition-related incidents around the five girls have been resolved, Koyomi Araragi's two risky younger sisters – the self-proclaimed heroes of justice, Karen and Tsukihi – become involved in some trouble.

Kaiki heads to North Shirahebi Shrine daily in order to deceive Nadeko the snake god but finds himself being followed on his way home. Furthermore, he gets a mysterious threat telling him to “pull out of this case.”

After the graduation of Araragi and Senjougahara, Suruga alone to deal with her left hand that has been turned monsterous from her mother's monkey paw charm. After hearing rumors of a "Devil" that can solve one's problems no matter what, Suruga set out to find this person.

After having her hand healed, Suruga has many questions for her former classmate Rouka. She was unable to contact her, however a meeting with Keiki Deshu, who seems to have survived the attack from the previous season, answers some questions of hers.

Suruga realizes that the collector is in fact Rouka, and she has been collecting parts of the "devil" as she feeds off the misfortune of others. Her motives are questionable...

Rouka challenges Suruga to a one-on-one basketball match as the two discuss the events that led up to their collection of their respective "devil" parts. Suruga is still coming to terms with the ability to use her left arm again.

Upon finding the Demon's head, she meets Rouka once again. Instead of giving the head to Rouka, she refuses. She is unable to stand the sight of her because of the fact that she can see her as she is a ghost. Suruga then challenges Rouka to one-on-one basketball in a wager for the head if Suruga loses.

Koyomi Araragi and Shinobu Oshino discuss the true nature of Shikigami doll Yotsugi Ononoki, and Koyomi is being rudely woken up by his sisters who tell him to cram for his upcoming college entrance exams.

Koyomi Araragi sees that he has no reflection, and discusses this with Shinobu. She then suggests that Koyomi should see Yozuru Kagenui and Yotsugi Ononoki.

When Yotsugi tells Koyomi that he is indeed becoming a vampire, Koyomi reasons that using his vampiric powers must have come with a price. Yozuru tells him that while there is no way to undo the progress of his transformation, there is a way he can stop it from progressing further: he must no longer use his powers as a vampire. However, this turns out to be quite a challenge when he learns his sisters and Suraga have been kidnapped.

Koyomi and Yotsugi land at the base of the mountain, where they are surprisingly met by Ougi Oshino. She talks with Koyomi for a while about his current situation and his upcoming confrontation with Teori. Koyomi and Yotsugi begin their journey up the mountain.