Hanahaki Disease [花吐き病]

Hanahaki Disease [花吐き病]: An illness born from one-sided love, where the patient throws up and coughs up flower petals when they suffer from one-sided love. The infection can be removed through surgery, but the feelings disappear along with the petals. 

The term hanahaki comes from the Japanese words hana (花), which means "flower", and hakimasu (吐きます), which means "to throw up". The disease is also named after the first known pair to both suffer from this disease. Hana and Haki, two college students from Japan.

It often develops over months or even years, beginning with coughing up a few petals and growing in intensity (and pain) until the victim is vomiting entire flowers, by which point the disease has entered its final stages.

If the object of the victim's love returns their affections, thus making the love no longer unrequited, the victim is then cured of the disease but if the victim cannot believe that their beloved returns their love, they will die. They die when the victim's lungs get filled with the flowers and roots grow in their respiratory system. They choke on their own blood and petals, and die.

The flowers can be surgically removed, but the victim's feelings of love will disappear too, meaning they can no longer love the person they once loved. Sometimes this also removes their memories of the former beloved, or the victim's ability to ever love again. Often, the one suffering the disease will refuse the surgery, preferring to die rather than losing their feelings.