Tohru Honda is the main character of Fruits Basket. She's very dim but all heart (and has some pretty impressive angst for a fluffheaded shoujo heroine) and has giant, empty eyes that threaten to suck out your soul. I love the girl, but there isn't much upstairs, and that art makes her look like a genius.

(For some strange reason, I suddenly wanted to compare her to Orihime, though I don't know why. They're both big hearted and smarter than they initally appear[though intuitive is probably more accurate in Tohru's case] but really not very alike.)