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Tomoe and Mio are Expy or alternative versions respectively of Smaugh and Ungoliant, from Tolkien's Legendarium.
Especially Mio.
Tomoe appears initially more similar to a Chinese dragon than to Smaug, and she is related with mist and water and not with fire; moreover, Chinese dragons are able to assume a human form.
On the other hand, Mio is initially a giant ravenous alien black spider-thing related with darkness and hunger (hunger of everything). More Ungoliant than Shelob: Shelob does not appear interested in rings or gems, Ungoliant would have eaten everything, also the Silmarils.
Mio is an alien.
She appears (moderately) interested in anime and science fiction. Moreover, her underlyings appear as shape-changing bug aliens.