Tenki no Ko follows Hodaka Morishima, a runaway high school student who arrives in rain-soaked Tokyo determined to survive on his own, even if that means taking a low-paying job at a small-time publisher and living on the edge of the city. In the same Tokyo, Hina Amano is an orphan struggling to support herself and her younger brother while the endless rain turns daily life into a burden for everyone around her.
Their paths cross when Hodaka tries to rescue Hina from shady men, and the two decide to run away together. Before long, Hodaka discovers that Hina has an astonishing and mysterious ability: when she prays, she can call out the sun and push the rain away. In a city where the sky seems stuck in gray, that gift makes her a kind of "sunshine girl," someone who can bring brief relief to the people of Tokyo when they need it most.
At first, Hina's power seems to offer both of them a way forward. But as Hodaka becomes more deeply involved in using that miracle, the story makes it clear that every change in the weather comes with a cost, and that the price of a brighter sky may be far greater than either of them can afford.