In a Tokyo drenched by relentless rain, Hodaka Morishima, a runaway high school student, fights to survive while working at a small publishing company. Hina Amano, an orphan striving to support her younger sibling, is also searching for employment.
Their lives intersect when Hodaka saves Hina from a group of menacing men, and the two flee together. Hodaka soon discovers that Hina holds a unique power: through prayer, she can summon sunshine. Observing Tokyo's peculiar weather, Hodaka sees an opportunity and proposes that Hina become a "sunshine girl," using her ability to bring light to people during difficult times.
While their circumstances initially improve, they soon realize that wielding such power carries severe consequences.