In Ano Natsu de Matteru, a strange summer encounter changes the ordinary life of Kaito Kirishima. One night, while testing his camera on a bridge, he sees a blue light streak across the sky before being blown from the railing. In the seconds before he loses consciousness, a mysterious hand reaches down and pulls him to safety. By the next morning, Kaito is back in his room, unharmed, but with no memory of how he survived the fall or what really happened that night.
When summer break begins, Kaito and his friends decide to use his camera to make a film together. What starts as a simple school project soon becomes the center of a memorable season, especially after Tetsurou Ishigaki invites the upperclassman Ichika Takatsuki and her friend Remon Yamano to join them. As the group spends more time together, their shared work on the film brings out awkward feelings, hidden hopes, and the tension that comes with growing closer. With the warm days of summer passing quickly, Kaito and the others find that their project is becoming much more than a movie, pushing each of them to face what they feel and what they want from one another.