On a spring night in Tokyo, university student Kakeru Sorano carries emotional wounds that have led him to avoid deep relationships. At a welcome party he is reluctantly dragged to by his dorm roommate, he meets Koharu Fuyutsuki, a cheerful and warm woman who laughs often and speaks passionately about her dreams. What Kakeru initially does not realize is that Koharu is blind, having lost her sight due to an illness. Despite her visual impairment, she attends university, shows interest in clubs, makes friends, and lives with a determination that stands in stark contrast to Kakeru's own withdrawn nature.

The story is set primarily on a university campus in Tokyo, where Kakeru finds himself drawn into Koharu's world. After he picks up her white cane following a class, the distance between them begins to shrink. As he starts helping her with her coursework, Kakeru is gradually touched by her brightness and positive outlook on life, while Koharu finds herself attracted to him precisely because he treats her naturally and without the special consideration others often give her due to her blindness.

A notable narrative arc centers on one specific item on Koharu's bucket list, which she keeps written in Braille on a bookmark: she dreams of launching fireworks. This wish puzzles Kakeru, as she cannot see them, but he becomes determined to help fulfill it nonetheless. The goal of launching fireworks becomes a catalyst for Kakeru to begin confronting his own fears and past trauma, while for Koharu, the memory of seeing fireworks before losing her sight represents hope and a way to face the future.

Supporting characters include Ushio Narumi, Kakeru's loud and friendly roommate from the Kansai region who often finds himself confused by Kakeru's reluctance to connect with others, and Yuko Hayase, Koharu's supportive friend who is also Kakeru's childhood friend and knows about his past. Additional cast includes Koharu's doctor, who tirelessly searches for treatments, and her mother, who cares for her without showing signs of distress. The live-action series follows Kakeru and Koharu as two people searching for light, weaving a delicate love story about a boy who has shut himself off and a girl who cannot see but refuses to give up on life.