In June 2021, Hodaka Morishima, a freshman in high school, escapes his troubled home life in Kozu-shima by heading to Tokyo. His journey takes a dramatic turn when the ferry he is on encounters a torrential rainstorm, during which he is saved by Keisuke Suga. Struggling to find work in the city, Hodaka stumbles upon an abandoned Makarov PM handgun in a trash can.
As he navigates this difficult life, he crosses paths with Hina Amano, a kind-hearted employee at McDonald's who offers him food out of compassion. Suga later hires Hodaka as an assistant at a small occult magazine where they explore urban legends tied to the unusual rainy weather affecting Tokyo, including the tale of "sunshine girls," who supposedly possess the power to control the weather.
One fateful day, Hodaka witnesses Hina being coerced into working at a club. When he attempts to step in, he finds himself confronted by the club's owner, leading to a tense situation where he loses control and fires the gun—thankfully, missing. Hina quickly leads him to Yoyogi Kaikan, an abandoned site with a shrine on the roof, where he discards the weapon after realizing the weight of his actions. It’s then that Hina surprises him by using her ability to clear the sky through prayer.
As the story unfolds, Hodaka learns that Hina supports her younger brother, Nagi, and they lack adult supervision. Recognizing their shared financial woes, Hodaka suggests they create a service to clear the weather for events, which quickly gains popularity. However, their business takes an unexpected turn when Hina appears on television after a successful job clearing the sky for a fireworks display, resulting in an overwhelming demand for their services. Feeling overwhelmed, they decide to pause operations to recuperate.
Meanwhile, the police have been on the lookout for Hodaka as a missing person's report has been filed by his family. They identify him via security footage connected to the gun incident, prompting an investigation that directly impacts Hina as she realizes she and Nagi could be separated by social services due to their lack of guardianship. After a police visit, Suga, wary of the growing suspicion, dismisses Hodaka from his job.
In a desperate attempt to evade capture, Hodaka, Hina, and Nagi try to escape but are thwarted by worsening weather conditions. The situation escalates when two police officers confront them; however, in a moment of surprising power, Hina inadvertently unleashes a bolt of lightning, allowing them to escape. Taking refuge in a hotel, Hina reveals the toll her abilities are taking on her, explaining that her transparency increases with usage—her sacrifice is necessary to restore balance to the weather.
The next day, Hina mysteriously disappears, and the rain ceases. Hodaka, taken into custody, learns that Nagi has been sent to a children's counseling center. Realizing his profound love for Hina, he escapes with aid from Natsumi Suga, Suga’s niece. With Suga’s help, Hodaka reaches the rooftop shrine where he leaps through the shrine gate, ascending to the skies to find Hina. He implores her to release her burdens and prioritize her happiness.
Upon their return to the shrine, they all find themselves arrested, while the heavy rains resume. Subsequently, Hodaka is sentenced to three years of probation and sent back to Kozu-shima. Fast forward to three years later, Tokyo remains submerged due to the continuous downpour. In the spring of 2024, having completed his probation, Hodaka graduates high school and returns to Tokyo. He reconnects with Suga, who has expanded his business and encourages him to search for Hina.
Finally, Hodaka discovers Hina praying on a street that overlooks the flooded city. In a heartwarming reunion, he promises her that they will find a way to be alright together.
