Amane Fujimiya is a socially awkward first-year high school student who lives by himself in an apartment. His neighbor is schoolmate Mahiru Shiina, a girl who is so beautiful and so unreachable that the other students call her an "angel." On the way home one day, Amane notices Mahiru sitting alone on a park swing, drenched in the rain, so he lends her his umbrella. When Amane catches a cold the next day, Mahiru insists on taking care of him, and the two next-door strangers embark on an unusual new relationship.