Aku no Hana is a Japanese manga written and illustrated by Oshimi Shūzō. It was serialized in Kodansha's Bessatsu Shōnen Magazine from September 9, 2009 to May 9, 2014, and is licensed by Vertical in North America. The story is about a middle school student named Kasuga Takao, who is forced into a "contract" by a classmate Nakamura Sawa after he is caught stealing his girlfriend's gym clothes. In love with Saeki Nanako, the trio's troubled, complicated school life has since begun. The title of the manga is based on the poem book Les Fleurs du Mal by Charles Baudelaire.
The manga received a nomination at the fifth Manga Taishō Awards. An anime television series adapted from the manga produced by Zexcs, aired in Japan from April to June 2013. It was co-aired outside of Japan by Crunchyroll. The show used rotoscoping techniques, causing some controversy among manga fans. The series has been licensed by Sentai Filmworks.
A live-action film adaptation was released on September 27, 2019.
The story begins in a small town in Gunma province  and follows Kasuga Takao, a middle school nerd with a fondness for the poem Les Fleurs du mal by Charles Baudelaire. One day after school, in an impulsive minute he stole gym clothes from Saeki Nanako, the classmate he secretly loved. However, another classmate named Nakamura Sawa caught him and forced him into a "contract". At that time, Kasuga grew closer and closer to Saeki and became her boyfriend.
As Kasuga spends more time with both girls, he feels the guilt of the perverted thief's behavior weigh on him. He tried to confess by ruining his class with Nakamura but Saeki still didn't want to cut ties with him. When his mother found out that he was the culprit of the vandalism, he left the house and tried to ride his bike to hide with Nakamura across the mountain adjacent to the town. Saeki caught up with the couple as they rested and found ways to get Kasuga back. Unable to choose between either, he rejected both; the police came and got them back.
A month later, Kasuga broke up with Saeki and resolved to help Nakamura because she felt her situation was pitiful. He has created a work to express his feelings for her. When she ran away from him, Kasuga went to her house and stole the diary showing her dissatisfaction at not being able to reach "the other side". He stole the underwear of all the girls in the class except Saeki and used them to decorate the temporary hideout in order to win Nakamura's heart.
When the summer vacation started, they came up with a plan to nail their panties to a piece of plywood for display at the upcoming festival. Saeki discovers his plan and lures Kasuga into his hideout, tries to seduce him and advises him to stay in their town. When he announced that he chose Nakamura over her, she raped him but was still met with fierce resistance from Kasuga that forced her to set fire to the hideout.
Saeki later confessed to the police about her fire behavior causing best friend Kinoshita Ai to tell their school about Kasuga's crimes. The school didn't want to mess with the police and his parents decided to move to another place to live after the vacation. The day before the festival, Nakamura broke into Kasuga's house, attacked his father and the two fled together. At the festival, they do not disguise and climb to the stands holding knives. They cursed their whole town and attempted to set themselves on fire. But before they could use a lighter, Nakamura pushed Kasuga out of the stands and she was kicked out from there by her father as well.