Matsuri

Matsuri is a new, anime-exclusive, character.

Appearance
Matsuri is an invisible high school student, but in episode 13, she is depicted as red haired and blue eyed student after Tetsuo Takahashi touches her face to feel her facial features.

Personality
Matsuri is perfectly comfortable with not wearing clothes, as she's invisible; although she notes another invisible person she met felt the opposite. However, she doesn't seem aware of how socially awkward this is, as no one knows where her face is.

Trivia

 * It is unknown if Matsuri is able to see herself (as other cartoon and anime suggest invisible people can see their features when other people can't).
 * Its logical to assume Matsuri wears clothes in cold weather.