Huh, this is a tricky one because there's a couple of books with that title, isn't there? Assuming we're talking about the historical fiction one set in post-war Japan, the central duo is definitely Akari and Shin. Akari is this young woman trying to rebuild her family's kimono shop, and Shin is the stoic, slightly damaged soldier who comes to work for her. Their dynamic is the whole engine of the story.
You also can't forget Old Man Sato, the neighbor who acts as a grumpy but wise mentor, and Akari's younger sister, Emi, who represents the new, modern Japan pushing against tradition. Emi's subplot with a young American journalist adds a whole other layer. Honestly, Shin's war flashbacks and his strained relationship with his own family back in the countryside sometimes feel more vivid than the main romance, at least to me.