Magister Negi Magi - Mahō Sensei Negima!!

Yume Miru Kikai (Dream Mill and Machinery) (1x16)

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Chachamaru malfunctions, and when she "wakes up", she discovers she is a normal, living human. She enjoys being human, particularly the ability to change her hairstyle. However, when she wakes up for real, she discovers it was merely a dream. Meanwhile, Fei Ku and Satsuki become the latest to disappear.