Kaoru has Xeroderma Pigmentosum, a medical condition that forbids its bearer from being exposed from direct sunlight. She sleeps during the day, and is active at night. She busks every night in front of a station, playing the 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 medical condition. He is Kōji Fujishiro. When her friend drags her home, they sit by her window, while they watch Kōji meet his friends. Kaoru explains everything, and her friend notes that she probably goes to the same school as him, and offers to spy on him for her.