Kodomo no Asobi

The protagonist in Kodomo no Asobi has been suffering from a weak constitution ever since childhood. The cause of this is a strange curse that was placed upon him. Then when a new spring arrives he is just about ready to accept his fate of living with it for the rest of his life, unable to see a way out of this. It’s at that time that he meet “that person”. Even though she seems to know about him, he doesn’t remember meeting her before. She tells him that even after so many years, the feelings inside of her haven’t changed at all. She still loves him so much that she can no longer bear it. However, she says all of this with a disappointed look on her face. What’s going on here?