Basic Story of Madoka Magica from Wikipedia - SPOILERS
★ In this world, there exist strange creatures who have the power to grant one wish to a chosen girl. However, in exchange, that girl must then become a magical girl and use her powers to fight against witches, evil creatures born from darkness that are responsible for murders and suicides.
★ In the city of Mitakihara, a schoolgirl named Madoka Kaname and her friend Sayaka Miki are approached by a familiar named Kyubey, who offers to grant each of them one wish in return for making each of them a magical girl. Another magical girl named Homura Akemi tries to prevent Madoka from making such a deal, while Kyubey urges Madoka by telling her she will become the most powerful magical girl. However, contrary to the glamorous notions one would expect, a magical girl finds herself dealing with death, isolation, loss of humanity, agony over the value of her wish, and existential crisis. Madoka, following her friends, soon sees the darker side of being a magical girl, and because of knowing the truth about being a magical girl, she questions if she should become one as well.
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The End of the Series and Epilogue - MORE SPOILERS
★ Madoka makes her final wish: "I wish to erase all witches from existence before they're even born. Every witch in the universe, from the past and the future, with my own hands". As promised by Kyubey her wish is granted and she becomes a goddess, breaking the Incubators' system at the same time. Madoka is seen traveling through space and time, healing defeated magical girls.
★ The consequence of her becoming a Magical Girl quickly follows the "rescue" of the other magical girls: due to her wish, the laws of nature have been altered, and the old world will be put to an end in order for a new one to take its place. Homura witnesses the Earth being swallowed in despair from the moon, where she also sees Madoka's soul gem, now the size of an asteroid, traveling through space.
★ The gigantic soul gem collapses into a Grief Seed and Madoka's new planet-sized Witch form is unleashed: However, true to her word, she erases her own Witch self from existence. The resulting paradox removes Madoka from the universe.
★ The cosmic sequence continues with Madoka losing her physical humanity to become a force of nature, detached from mankind; however, she is now suspended in interdimensional space, in contact with everyone and everything.
★ However, the concept of harvesting witches for energy would be more efficient than the new method: because there is still grief in the world, it manifests in the form of demons that the magical girls must fight, who upon defeat drop cube-shaped pieces much like Grief Seeds.
Now
★ Magical girls and boys are still needed to fight demons. Like before, to become a Puella Magi they must make a wish, and thus create a contract. Now, they make that contract the with Holy Mother Madoka. In exchange for their wish being granted they gain the abilities of a Puella Magi and fight the demons of the world. If they ever decide that they are too tired from fighting and stop collecting Grief Cubes, they will die.
