What shoujo manga is this?

I don't remember much, but it's basically about this girl, who is always alone in the library. She is a bit timid and one of the boys in her class harshly criticized her for it; from that day on she's been scared of that boy. The library is basically her refuge, and one day, she found a letter in one of the books, she ended up writing a reply to the letter and tucking it in the book. Surprisingly, she got a reply to it o.o and that's how their correspondence started. If I'm not mistaken, she thought that she was corresponding with this gentle boy that she liked, but it turned out it was the boy that she found scary. He was a tsun2x I think and in reality had a crush on the girl hahah. I remember a scene where the boy was playing soccer (?), and he would always see the girl by the library window. I think he maybe liked the way her expressions changed while she was reading the book (?).
Sorry for the fuzzy memory XD