(pathology) collagenosis, collagen disease

meeting all three important requirements

(fiction) Hanahaki, an illness affecting those consumed by unrequited love that manifests as the coughing up of flowers, which clears up upon reciprocation. A fictional illness, it has found popularity among both Japanese and foreign online fanfic (especially) artists and authors for its poetic quality.

flat / level / even / smooth

精神分裂病:

to go; to come to one's place / to (a letter) be delivered / to depart / to rely (on a method) / (年が～) to age / (うまく～) to go well / イく: (slang) to have an orgasm, to come, to cum

sacrifice

silkworm

physical education / (by extension) physical exercise

education