Synopsis

A youth coming-of-age romance story that the depicts young people connecting beyond history, culture, and national borders.
 
Set in Karatsu, Saga Prefecture, the story follows high school student Tatsuhiko, who spends his days obsessed with fishing. His routine begins to change when Yoonseul, an exchange student from Busan, joins his class, prompting him to wonder why she chose Karatsu as her study-abroad destination.
 
As the two grow closer through their time together, the reason behind her decision gradually comes to light. However, after being hurt by an offhand comment from Tatsuhiko, Yoonseul suddenly returns to Korea. Meanwhile, Tatsuhiko measures the distance between Karatsu and Busan on a map in his textbook and realizes the gap between them is only “3 millimeters.” That discovery leads him to make a life-changing decision.