Hanahaki Disease is a fictional disease where someone begins coughing up flower petals because they have unrequited feelings for someone. The flowers can grow in the stomach, lungs, or heart, though it is traditionally in the lungs. Hanahaki Disease is a painful, slow disease that often develops over months, if not years, and begins with coughing up a few petals, and grows in intensity and pain until the victim is coughing up entire flowers, at which point the disease has reached its final stages. If not treated, the disease is fatal. It's primarily an online phenomenon that appears in Fan Works, but it has appeared in original works as well.
Hanahaki Disease originates from Japanese works. The word "hanahaki" is a fusion of the Japanese words "hana" (flower) and "hakimasu" (throw up). The first usage of the trope is unclear, but it was popularized in Japanese Yaoi Genre fandoms before spreading to Korean fandoms and then other international fandoms.
This trope is popular because it has a lot of melodramatic angst-potential, while also being pretty. Death by Hanahaki Disease is tragic but beautiful. The victim is killed from within by something as beautiful as flowers. Haunted by their unrequited love, the person usually tries to cover up their illness. They'll leave behind trails of bloody flowers, which are both horrific and aesthetically pleasing. Flower Motifs are often used, which adds to the symbolism. The flowers are frequently associated with their unrequited love interest: it could be their favorite flower, their favorite color, a flower they're named after, or something along those lines. (So, for example, if Bob is in love with Sakura, he might cough up cherry blossoms.)
Despite how deadly Hanahaki Disease is, it can be instantly cured if it turns out the other person likes the dying person back. It can also be cured by surgery, but this cure often means that the person will lose their feelings for the person they love (a double-edged sword which amps up the drama). If, for some reason, it can't be cured, it sometimes can be managed with medication (though this is not seen too often), but it never fully goes away.
- In the Warrior Cats fic Bluebells, Leafpool gets the disease because of Mothwing. She initially thinks it's greencough/pneumonia, but she begins coughing up flowers alongside blood. Eventually Leafpool begins sprouting flowers out her chest. Right before she dies, she confesses to Mothwing, who says that she likes her back. This cures Leafpool of her Hanahaki Disease. There is also a Multi-Animator Project based off of the fic.
- The Taste of Dirt is a Riverdale oneshot where Archie and Veronica begin vomiting and coughing up flowers because they're in love with Jughead and Betty respectively.
- Sonic the Hedgehog Slash Fic Hanahaki Disease is Exactly What It Says on the Tin, about Sonic coughing up pink rose petals because of his crush on Shadow. Also doubles as a Coming-Out Story due to Sonic being raised in a stigma around homosexuals.
- The Splatoon oneshot i'm so full of love i can hardly breathe is about Pearl suffering with the disease because of her feelings for her best friend Marina.
- When The Flower Blooms is an animesque original short based on this trope. It's about a teenage girl who becomes sick with the disease. She begins coughing up bloody cherry blossom petals. It turns out that she's dying of a known terminal illness that comes with unrequited love. She's cured when her Love Confession is accepted, however her best friend gets sick with the disease.