Hakubo follows the everyday routine of Sachi Koyama, a promising high‑school violinist. While she enjoys her studies and keeps close friends in the music club, her preferred leisure is strolling solo to the bus stop, taking in the sights of Iwaki"s streets. One after‑school walk brings an unforeseen encounter with Yuusuke Kijinami, a boy she frequently sees on her commute home. Sachi offers to help him locate the ideal spot for the sunset view he plans to paint for his art club"s upcoming show. Their shared love of twilight scenery quickly creates a connection, and the two become friends who cherish each moment, fully aware that such beauty can vanish in an instant. They both understand that time slips away like the last rays of sun, so they decide to document these fleeting scenes together in their diaries.
