There's no way to know exactly without reading the 'Accelerator Love Story'. But they could be a young couple who find themselves in a situation involving an accelerator. Maybe one of them is an inventor or engineer who is working on an accelerator project, and the other gets drawn into their world, and that's how the love story begins.
Since I don't have the actual story, I can't say for sure who the main characters are. They could be two scientists if the accelerator is a scientific device. Or they could be just ordinary people whose lives are affected by something related to an accelerator.
I really don't have enough information to name the main characters. However, they might be characters from different backgrounds. For example, one could be from a technological background, deeply involved with accelerators, and the other could be an artist or a writer who is introduced to the world of accelerators through the first character. Their different outlooks on life could create an interesting dynamic in the love story.