Kaoru has Xeroderma Pigmentosum (XP), and is not allowed to be exposed to sunlight. She sleeps during the day and is active at night. She busks every night in front of a station playing guitar. Outside her bedroom window, she spots a high school boy with a surfboard. She watches him and his friends visit the ocean every morning, before going to sleep. One day, she introduces herself to him without letting him know about her illness. He is Kji Fujishiro (Takashi Tsukamoto) When her cousin drags her home, they sit by her window while they watch Kji meet his friends. Kaoru explains everything, and her cousin notes that she probably goes to the same school as him, and offers to spy on him for her.

The next evening she sits by the bus stop. Kji arrives on his scooter. Both embarrassed, they start talking and Kji eventually promises to meet her and listen to her sing another night, at the start of the school holidays. When they meet up, another obnoxious street performer has taken her spot. Kji decides to take her to the city, where after seeing the sights, she starts playing in a square. (YUI's music video Skyline features this event). A substantial crowd gathers to hear her sing. Afterwards they watch the ocean, and Kji asks her out.

Their date, however, ends abruptly as the sun breaks out and Kaoru flees home. Kji is soon informed of Kaoru's condition and is taken aback. For a while, Kaoru stubbornly refuses to see him. Kji learns of a recording studio where Kaoru could record her debut single, and takes up small jobs to earn the money to pay for it. Her father, out of concern, invites Kji over one night. At dinner, Kji reveals his plans for Kaoru's CD. As they walk home that night, the two begin to talk and Kaoru slowly realizes how much Kji truly cares for her.

As her disease worsens, she loses feeling in her hands and is unable to play guitar. She assures Kji that she still has her voice.

In the studio, she asks her family and friends to leave. She asks them to wait for the CD.

Time passes. As promised, Kji brings Kaoru to the beach to watch him surf. The protective suit she had left hanging for years is finally used. By now she is in a wheelchair. She complains that the suit is getting hot. With a painful expression that fades quickly, Kaoru's father tries to convince her that if she takes off the suit, it can't bother her anymore, that she could run around freely. She declines. With that, she struggles to stand up and limps weakly toward Kji. As she walks, she trips over the sand and Kji rushes to catch her. She catches herself at the last minute, revealing that it was a feint and giggles at his surprised face.

Finally Kaoru is laid to rest in a coffin full of sunflowers. Kji, Kaoru's friends and family listen as Kaoru's CD is finally released. In the final scene, Kji rushes towards the waves, his mind replaying her voice.