The Parallel World Pharmacy manga is an adaptation of an original light novel series. The story starts out with Kanji Yakutani, a revered medical researcher who keeps himself insanely busy with work, and who is haunted that nothing could be done to save his younger sister from dying from a brain tumor. Yakutani works so hard, in fact, that he works himself to death in his thirties. He awakens as a 10-year-old boy named Farma living in a medieval-esque fantasy world.

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