What manga is this???????

there was a girl who looked like a teenager but she was in elementary school. she was pretty. and there was this boy who she knew when she was younger. she use to always watch him play basketball and claps for him. she is now living with him, i think? the person the boy likes is going out with another person. but no one knows (i think). the boy gives the girl a chance. but one day, when the boy finds eavesdrops on the person he likes and the person who is going out with her, either the boy or girl (probably girl, because the boy was behind her so she couldn't see him) said she liked him. the girl ran away, the boy chased her, and the elementary girl was right outside the building and she saw what happened. then she just cried and cried. and said something about god being cruel. :/