The manga is about a girl who sits in the bench in classroom near the window and a random student shows up outside at the other side of the window and starts talking to her. Every now and then he shows up and talks to her and she starts to develop feelings for him. One day he stops showing up and she realized he was in the hospital. She goes there to meet him and they hug or something. He was like really ill and he left the hospital every day to see her near the window. They end up together at the end.
I am almost sure it is one-shot manga, definitely shoujo, school-life. I've read it few years ago, It's not really a new manga. The art is really pretty ^^. I know the main girl character has black hair.
I would be so happy if someone can recognize that manga and tell me the name. I'm kind of desperate. Thanks! <3