The idea was originally found in A_Bored_Reader Undertale ideas for stories that hit me like the brick called Reborn! I asked permission to use it. Read the original if you're interested, but it contains quite a few spoilers for this story.
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Warnings: Heavy themes, illness, death of supporting characters, mention of self-inflicted wound, the loss of a brother, the growth of flowers can be somewhat grotesque, self-hatred and helplessness.]
Sans or Skyflower didn't have many memories of the war as children, just blurry memory fragments. The clamor of shouts and fights, the dust of the dead filling the air, the bloody corpses of the enemy lye everywhere. Gaster fought in the front line, while hold his wrapped up little brother he run away with the other children's. The virus exploded like a bomb scattering its spores, sweeping away everything around it. Skyflower fell from the shock wave and curled up to protect his brother with his own body. It was all in vain, by the time he regained consciousness, they were already under quarantine and even if they showed no signs of the disease, they were not allowed to leave the quarantine... His energetic younger brother was the ray of light for many of them, who contributed to the fact that the brothers grew up helping patients.
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[Underflower Papyrus]
Sans also participated in the research of the disease as Gaster's assistant. Gaster's dying was traumatic, and he panicked when the first flowers appeared on his wings... The disease slowly and painfully covered its victims with flowers. The uncomfortable, painful feeling as a tiny flower made its way through his feathers, which, struggling with his tears, he pulled out with his own hands to get rid of the traces. When Frisk joined the researchers, half of his face was already covered in tiny purple flowers. The flowers could vary depending on the person, for example Frisk had small yellow flowers growing in her hair. After discovering the Reset, Frisk used it to find the cure.
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– Everything is okay! I'll beat it in no time! After all, I am the wonderful Papyrus! – his younger brother posing with a smile in the hospital bed, while blood was flowing from his eye, from which sunflowers grew.
– I know Papyrus, you're the best – Skyflower trying to be supportive, while he was ready to crumble at any minute from the mere thought of watch him as slowly and painful dying. His brother rewarded his words with a smile before wincing in pain and the sound of bones cracking as the stems of the flowers made its way.
