A pair of childhood friends who grew up together could also be the main characters. As they grew older, their feelings for each other started to change into something more romantic. However, misunderstandings arose. Maybe one misinterpreted a friendly gesture from the other as a sign of disinterest. And before they could clear things up, one of them had to leave town due to some family emergency, and their love story was left unfinished.
They could be two young students who fall in love at school. They share the same interests in academics and extracurricular activities, but then face challenges when their families plan to move to different cities.
I'm not sure as I haven't read the book specifically. But generally in a love story, the main characters could be a young man and a young woman. Maybe they are from different social classes or have different life goals that create the conflict in their relationship.
It could be an old man who used to be a toymaker. He was in the process of making one last special toy for Christmas but didn't finish due to his old age and failing health. The story could be about his memories and the importance of his final creation.
It could be a group of coworkers. They work in a competitive environment, and there are rivalries, alliances, and betrayals among them. Their stories are full of drama and emotion, just like in a love story, but there is no romantic love involved.
Perhaps one of the lovers sacrifices their own happiness for the other. Say, one is in a difficult situation like a serious illness, and in order not to burden the other, they choose to break up. This would be a very bittersweet ending to the unfinished love story.
There could be a young, adventurous dolphin called Dash and an older, wiser dolphin known as Pearl. Dash's energy and Pearl's experience create an interesting dynamic as they fall in love. They teach each other things about life in the ocean and their relationship grows.
It could be a young adventurer and an old wise hermit. The adventurer stumbles upon the hermit's dwelling during one of his expeditions. Despite the age gap and different outlooks on life, they form a deep bond that neither of them expected, which is an uncharted kind of love.
The main characters could be two goldfish. One is a bright orange goldfish and the other is a shiny white one. They meet near the little castle in the aquarium and start to develop feelings for each other.
It could be two cyborgs. One cyborg might be an older model, more mechanical in nature, and the other could be a new, more advanced model with more human - like features. They might fall in love as they learn from each other and discover new things about their own existence.
The main characters could be the lead violinist and the orchestra's composer. The violinist is always the star performer, and the composer is constantly writing new pieces for the orchestra. They start collaborating closely, and soon, their professional relationship blossoms into love.