Miki, Sayaka

Witch (later in the anime)

Madoka's classmate who, after helping Madoka rescue Kyubey, ends up getting an offer to become a Puella Magi herself. She cares deeply for her friends, and wants to help an ill boy named Kyousuke Kamijou, whom she has a crush on. Before becoming a Puella Magi, Sayaka wields a baseball bat that Mami can enhance with magic to defend herself with while on witch hunts.

In order to cure Kyosuke's hand, which was damaged in an accident which robbed him of his ability to play the violin, she becomes a Puella Magi. Sayaka's weapon of choice is a sword. She also has regenerative powers stronger than anyone else due to the nature of her wish. Sayaka hates people who think only of themselves whilst hurting others and is easily provoked into a fight.

After learning how Puella Magi are created, Sayaka starts to descend into despair, as she believes she's now no better than a zombie and thus cannot openly admit her love for Kyousuke. Her state of mind only worsens as one of her two best friends, Hitomi, confesses that she has feelings for Kyousuke too and makes advances on him. At the same time, she also refuses to purify her Soul Gem with Grief Seeds and neglects it to become tainted. She rejects the grief seed provided by Homura Akemi assuming she has motives behind saving Sayaka. At the end of episode 8, her Soul Gem was finally exhausted, and Sayaka turns into the witch Oktavia von Seckendorff. She dies in a battle with Sakura Kyouko, who sacrifices herself in order to not let Sayaka die alone.

In episode 10, it's revealed that during Akemi Homura's third time loop, Sayaka also suffered the same fate of turning into a witch, and was killed by Homura with an explosive.

In Rebellion, Sayaka is sent by "The Law of Cycles', Madoka Kaname, to save Homura from becoming a witch. Homura, who is trapped in her very own labyrinth (her ideal world), is saved by Sayaka after fighting Mami Tomoe. Sayaka is interrogated by Homura about who had created this labyrinth and Sayaka asks her what she will do if she finds the witch of the labyrinth.

After Homura forces herself into becoming a witch into to save 'the Law of Cycles' from falling under the control of the incubator (Kyubey), Sayaka, Kyouko, Madoka, Mami and Nagisa rescue Homura.

Later after a new world is created by Homura Akemi, Sayaka reprimands her selfishness but is forced to forget any events from before. She tells Homura she might have forgotten everything else but knows that she is a Demon.