Kimi ni Todoke: From Me to You, Vol. 1 - Karuho Shiina
Originally I thought this was going to be similar to The Wallflower due to the main character being 'scary' and looking like she is the main character of a horror movie...however, this is not the case. The only thing that is similar is that both characters have long dark hair and are misunderstand. Oh and their names are a bit similar too.

Whereas Sunako loves the macabre and doesn't really want any friends (that are human) and shuns the 'bright' world. Sawako - who is nicknamed Sadako in kindergarten - is a loner who is actually quite nice and fairly optimistic. She wants to make friends. And then enters fate and a boy named Shota.

It's interesting to see Sadako grow as she leaves her isolated world and begins to interact with people. I am really digging the chemistry between the characters too.