Tsubame no Su, Swallow's Nest

One day, a transfer student joins her class. But while all of the other students gush over how gorgeous this new girl is, Tsubame is taken aback. Can’t you see, she has a bird’s head?! she thinks. It turns out that Tsubame is the only one who can see this girl’s real form. Everyone else only see the magical illusion that she cast on herself. Everyone else just sees Suu as a normal, but gorgeous girl. Tsubame wants nothing to do with her, but Suu latches onto her, as the only person that she can share her secret with, and from there, the adventures begin!

(Source: Living tall in Japan)