After accepting a weekend invitation, Hachiman Hikigaya accompanies Isshiki Iroha around the Chiba Prefecture to brainstorm ideas suitable for an ideal date with Hayato Hayama. As the duo wanders from place to place without a plan, they seemingly enjoy each other's company. Yet, through these straightforward and sincere interactions, the meaning behind what it means to be genuine continues to intrigue Hachiman and his outlook for the future of the Volunteer Service Club and its members. [Written by MAL Rewrite]

On Christmas Eve, Hiro Hirono runs into Miyako Miyamura, a frivolous girl who "borrows" his bicycle in order to chase down a purse thief. After Hiro finds his bicycle wrecked and Miyako unconscious, the two unexpectedly spend their Christmas Eve together, and when they discover they go to the same high school, their accidental relationship develops even further. This sparks the jealousy of Hiro's childhood friend Kei Shindou, whose pure approach to life catches the eye of Kyosuke Tsutsumi, a womanizing photographer searching for the perfect shot. Elsewhere, Renji Asou, a boy who dreams of being a girl's knight in shining armor, has a chance encounter with Kei's twin sister—the overly shy Chihiro Shindou, who spends her time reading alone—at an abandoned train station. The two quickly become friends and eventually decide to write a novel together. However, when Renji discovers Chihiro's secret, a disability that causes her to have an eternally ephemeral memory, his childish ideals will be put to the test. Guided by two mysterious adults, these youths' relationships intertwine in a heart-rending tale of love, rejection, acceptance, and memories.

Misaki Takahashi is a regular high school student who is preparing for his university entrance exams. In order to reduce the stress of studying, or so he hopes, he accepts the help of his older brother's best friend, and famous author, Akihiko Usami. However, Masaki is about to find out that Usami's books are of a very naughty genre, and that there may be something naughty waking up inside Masaki as well. Junjou Romantica also follows the story of two other couples loosely connected to Masaki and Usami's "Romantica." Egoist shows the very passionate, but often complicated, relationship between university professor Hiroki Kamijou (whose life has reached an all time low) and paediatrician Nowaki Kusama, who falls for Hiroki at first sight and would do anything to make him happy. The third story, "Terrorist," shows just how obsessive love can become when rich eighteen-year-old Shinobu Takatsuki finally discovers something that he cannot have so easily—the literature professor You Miyagi. There is passion abound as these three couples try to achieve their goals in life while also falling into temptation and anguish with their partners.

At the behest of the Queen, Earl Ciel Phantomhive hosts a lavish dinner party attended by several of the finest members of polite society—as well as struggling author, Arthur. But as the party reaches its high, a terrible murder takes place and none other than the Earl himself is suspected of the crime. As a violent storm rages on outside, the death count continues to climb. The Phantomhive household and their eminent guests find they must cooperate in order to solve this mystery before they too fall prey to the mysterious murderer. However, it seems that not even the perfect butler, Sebastian Michaelis, is safe from this horror.