Metamorphosis comes with the Sense of Sin

After the war, monsters were sealed under a mountain called Ebott. Only few of them taken as hostage to be lab experiments. Hundered years passed after the war. The Monster Kinds Project (MKP) banned because of the dangerous monsters trying to escape. Although, there was rumors about Monster Kind Project (MKP) was still continue in a hospital basement.

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~Meanwhile~
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(Y/N) woke up in a hospital room, doesn't remember why she was there or what happened.

She searched around and find a book close to her bed, near the dead flowers. The book was a dairy. A beautiful hand writing was explaining the horrible truth. She had a disease called 'Metamorphose of A Butterfly.' Writing explaned that she had 'a day memory store'. She could only have new memories on her 'one day' and when 24 hourse passed everything will start over again for her without the memories belong to yesterday.. Like a reset. But why was that only a day? Was it because (Y/n) coudn't survive longer than a day for some reason~ =)

[GasTale Sans x FemReader]
[I don't own the character, they are belong to their creators. Only the events in /story of the book is mine.]
[Multi-choose episodes]