The story takes place in a small town located in Gunma Prefecture and follows Takao Kasuga, a middle school bookworm whose favorite book is Charles Baudelaire's Les Fleurs du mal, after which the series is named. One day after school, he discovers and impulsively steals the gym clothes of Nanako Saeki, the classmate he has a crush on. However, a lonely girl named Sawa Nakamura happens to catch him in the act. Nakamura blackmails Kasuga into a "contract," under the threat of revealing his secret.
A middle school student who has a huge love for literature and a crush on Saeki. Upon seeing her gym clothes while alone in the classroom, Kasuga is unable to resist and begins scenting them, but then panics after hearing something and impulsively steals the girl's clothes. He soon discovers that his sinful act was witnessed by Sawa Nakamura, an isolated loner in his class who blackmails him into forming a contract, tying them as "friends". He many times has to bear the shame of her demands, but also acting on his own, begins to date Saeki himself, much to Nakamura's dismay. While initially disliking her requests and their meetings, Kasuga soon feels attracted to her personality, and realizes that Nakamura is actually lonely, longing to escape from the people of the town, much like himself. He develops strong feelings for her, promising to one day take her to the "other side". However, this causes him to break up with Saeki and hurt her feelings, which in turn brings a series of unfortunate events led by Nakamura's and Kasuga's schemes that increasingly cause havoc to their school, and soon enough, the whole town, Saeki's unwillingness to give up on him and the bare truth behind each person's character, a combination that eventually builds up until he is unable to control them.
Three years after the summer festival incident, Kasuga has moved to Ōmiya to restart his life. However, his family is now broken because of his past actions, himself becoming distant to his parents and society, and even losing the will to engage in literature. While having a few friends, he is quite reserved to the point of becoming awkward. One day, disillusioned with life and the parting with Nakamura, he encounters a colleague from school, Aya Tokiwa, purchasing Les Fleurs du mal in a bookstore, which leads to his return to the books, always lent by her. Despite her having a boyfriend, Kasuga becomes closer to Tokiwa, acting as an editor to her amateur novel, whose plot instigated and helped him bring up his resolve to actually restart his life and fix the mistakes he made. He manages to bring her to his side, promising to "kill her ghosts", and starts to date her. While sharing a good relationship after becoming lovers, Kasuga fears Tokiwa's interest in his hometown and refuses to go back there with her.
A classmate of Kasuga who sits behind him in classroom. She is considered by others as a strange, lonely and isolated girl, and reportedly has no friends. She shows no reaction to other people, and while remaining calm and apparently sane, she tends to talk back to others, calling people shit eaters. She is the sole witness to Kasuga's breakdown upon facing Saeki's gym clothes and, having knowledge of this fact, she blackmails him into becoming his "friend" if he doesn't want to let the school know his sin. She repeatedly calls Kasuga a "sick minded" person, vows to "peel off all of his skin" and forces him into shameful and torturous situations, displaying a sadistic personality. Nakamura has emotional outbursts when expressing herself to Kasuga, the only one aware of this weak side of hers, which leads him to deduce that her quaint behaviour is actually a demonstration of her desire to "escape" with him, ceasing to be alone and taking both "to the other side" of the mountains. Due to this, Kasuga learns to understand and earn Nakamura's admiration, and the two begin plotting together at one point of the story. However, Nakamura earnestly believes that even if Kasuga chooses to stay with her, she will ultimately be isolated.
Another girl from Kasuga's class, on whom he has a crush, Saeki is deemed as the top student of their class, and is considered to be a popular and beautiful girl. After he defends Nakamura from the rest of their class and supports him, Saeki begins to take an interest in Kasuga, especially his passion for Les Fleurs du mal and how he is able to show his true self, without having to hide his personality; desires or interests. The two start dating – contrary to Nakamura's orders to Kasuga – and Saeki reveals how she longs for a life in which she doesn't have to fake herself with being well-mannered, composed and focused on study. For this, she becomes determined to understand Kasuga better, but his increasing intimacy with Nakamura starts to make her jealous, and faced with a tough choice, Kasuga ultimately decides to side with Nakamura. While trying to win him back, she learns of Kasuga's and Nakamura's deeds, and becomes convinced that she corrupted the good person he once was. Obsessed with saving him from the evil acts of Nakamura, Saeki also begins to commit evil acts herself, mainly omitting her discoveries about the couple's schemes, but later unleashing her hatred over the bond Kasuga and Nakamura share, which eventually brings her disgrace.
Kasuga easily recognises Saeki in the city by her scent, which he has grown used to after stealing her clothes, on an occasion three years later. She now lives in Utsunomiya, has gotten a new boyfriend who, according to Tokiwa, "looks a lot" like Kasuga and later asks for the latter's e-mail. The two arrange to meet again and discuss the events from their pasts and what followed after the summer festival. Upon learning that Kasuga doesn't know about Nakamura's whereabouts, she toys with his emotions and reveals to be disappointed by his inertia and hypocrisy in life. She leaves for good, and upon meeting her boyfriend soon afterwards, shows contempt in being with him.
A character first introduced in the second part of the story, she is portrayed as a tall, red-haired beauty of Kasuga's year, revered by his friends, but known to date an older guy from another school. Kasuga notices her holding a Les Fleurs du mal copy on a bookstore and discovers her passion for books. She helps him regain his interest in literature once more, and becomes close to him, to the point of inciting her boyfriend's, Kouji, suspicion towards Kasuga. She accidentally reveals that not only she loves reading – a secret kept from her friends and boyfriend – but also dreams of writing a novel. She soon realises that Kasuga is the only one able to understand her, and also the only one she can relate to. At the promise of "killing her ghosts", she leaves Kouji and begins dating Kasuga, a relationship that becomes beneficial for both, as she is easily able to write her novel and he makes up with his parents. Tokiwa truly cares for Kasuga, and wishes to continue living with him on to university, but suspects he hides something from his past, as he irreducibly refuses her request for both to visit his hometown back in Gunma. Saeki notices Tokiwa's resemblance with Nakamura, and suggests she is only a replacement for her, certain that Kasuga will "throw her away when it gets too annoying" as she "is not Nakamura".
Saeki's best friend. Outspoken and hotheaded, she cares deeply for Saeki and begins to hate Kasuga for the pain he's caused her after breaking up. She latter gets the truth from Saeki when she realises her friend has been spying on Kasuga and Nakamura and becomes terrified by Saeki's omission. She feel the urgency to tell the police the deeds of the couple, only to be scolded by Saeki, who believes she'll be able to pull Kasuga out of his mess. As events develops and she realises Saeki's corruption as well, she is unable to hold out and becomes responsible for exposing Kasuga and Nakamura, but in the process also affects her best friend. Ever since the summer events in general, Kinoshita holds a grudge on Kasuga for his shameful and selfish behaviour.
Yamada is a friend of Kasuga's in middle school. He's a chubby guy, a blabbermouth mocker and doesn't understand Kasuga's fascination for Les Fleurs du mal. He actually plays only a minor role in the series.
The anime adaptation is directed by Hiroshi Nagahama and produced by Zexcs. It aired in Japan between April 5 and June 29 2013 and has been licensed by Sentai Filmworks in North America. Crunchyroll has the streaming rights in Australia, North America, UK and other territories. The Anime itself was animated using rotoscoping techniques, a decision that has caused some controversy due to the fact that the characters look more realistic, rather than resembling the original manga. The opening theme is "Aku no Hana" (惡の華?) by Uchūjin with guest vocalists Noko, Mariko Gotō and Shiho Nanba, while the ending theme is "〜花〜 A Last Flower" by Asa-Chang & Junray.
Kasuga is a literary nerd who goes to middle school in a small town. He idolizes Baudelaire and is in love with his beautiful and brilliant classmate Saeki. In his class there is also a redheaded outcast called Nakamura. One day after class, he returns to the classroom for a book he's forgotten, only to find Saeki's sports clothes on the floor.
"Flowers of Evil 2 of 13"
April 12, 2013
Kasuga steals Saeki's clothes. The next day his guilty conscience makes him uncomfortable in class. When riding his bike, he encounters Nakamura who tells him she saw him steal the clothes. The next day, she meets him in the library and blackmails him into following her orders. She pushes him into Saeki's breast and demands that he write an essay about the experience.
"Flowers of Evil 3 of 13"
April 19, 2013
Kasuga meets Nakamura after school in the library. He didn't write the essay Nakamura asked for. As a form of revenge, she undresses him and forces him to wear Saeki's clothes. The next day someone steals money in a locker. Nakamura gets accused. Because he was with her, Kasuga takes her defense. As a consequence, the class thinks he's in love with Nakamura.
"Flowers of Evil 4 of 13"
April 26, 2013
After school, Kasuga bumps into Saeki. She reveals that she thinks the way he defended Nakamura was pretty cool. Another day, Kasuga carries boxes for Saeki. He asks her on a date at the bookshop. Nakamura sees them and later forces Kasuga to wear Saeki's clothes underneath his own for the date.
"Flowers of Evil 5 of 13"
May 4, 2013
The date goes well. Nakamura, who's been following them, asks Kasuga to kiss Saeki. He refuses, asking Saeki to be in a platonic relationship. As she accepts, Nakamura dowses him in water, revealing the clothes underneath. He runs away before Saeki notices. Nakamura promises she'll stop interfering.
"Flowers of Evil 6 of 13"
May 11, 2013
The class learns of Saeki and Kasuga's relationship. Nakamura becomes friends with Saeki. In the library, Nakamura tells Kasuga that what Saeki really wants is to have sex with him. Saeki overhears her, and doesn't show up the next day. Kinoshita asks Kasuga to deliver handouts to Saeki. He goes and is taunted by Nakamura on the doorstep.
"Flowers of Evil 7 of 13"
May 18, 2013
Saeki thinks Kasuga might be with Nakamura, but when asked if hiding anything, Kasuga denies, and she decides to trust him. Kasuga then pleads Nakamura to tell Saeki the truth as he can't. Nakamura asks him to meet her in front of the school at midnight. She convinces him to write his deeds on their classroom chalkboard and then they proceed to extensively vandalize the room.
"Flowers of Evil 8 of 13"
May 25, 2013
Nakamura and Kasuga slowly walk home, hand in hand. The next day, the whole class is in uproar. The ink covered Kasuga's name. Saeki is devastated, her clothes at the center of the destruction. The whole school gets informed. Kasuga pukes. Saeki confronts him. He breaks up with her. She notices the drawing on the floor was the same as on his favorite book.
"Flowers of Evil 9 of 13"
June 1st, 2013
Saeki refuses to break up. The next day, Kasuga is absent. Saeki asks Nakamura what her relationship with Kasuga is. She says she's contracted to reveal his deviance. Saeki argues he's not a deviant. She goes to Kasuga's and make a case for him through the window. His mom finds his stained clothes and he runs away. Saeki sees his mom looking for him.
"Flowers of Evil 10 of 13"
June 8, 2013
Kasuga goes up the mountains with Nakamura on his bike. They stop because of the rain. Saeki goes looking for Kasuga and finds them. Nakamura undresses him again. When asked to choose between the two of them, he stands his middle ground and upsets both. A police car shows up because of Saeki's parents and brings them all home.
"Flowers of Evil 11 of 13"
June 15, 2013
One month later, summer. The three have been ignoring each other. On Kinoshita's initiative, Saeki and Kasuga talk, only to break up. Kasuga is a shell of his former self. His mother is upset. He pukes. He knows Saeki is going to be alright without him, but even in his dreams, he can't stop thinking about Nakamura.
"Flowers of Evil 12 of 13"
June 22, 2013
Kasuga writes an essay to Nakamura. Kinoshita asks Kasuga's friends what is wrong with him. Kasuga tries to give his essay to Nakamura, but she ignores him, so he starts reading it to her. She runs away. He goes to Nakamura's to deliver the essay. On the doorstep, he is invited in by the father who says he's her first friend.
"Flowers of Evil 13 of 13"
June 29, 2013
Kasuga enters into Nakamura's room. He finds her diary and starts reading it. He recalls what happened. Nakamura comes back, seizes the diary and runs away. He follows her and this time catches up to her. This time, he asks her to make a contract with him: they'll do what they can in order to leave for good someday.