Definitely fiction. Downton Abbey creates a fictional world with made-up characters and events, although it may draw inspiration from historical periods and social contexts.
In the 'akiza x yusei love story', Akiza and Yusei's love develops through their shared experiences. They often find themselves in difficult situations, and through working together to overcome them, their bond deepens. Akiza sees Yusei's determination and is attracted to it, while Yusei admires Akiza's unique qualities. It's a story of two people growing closer and falling in love.
Crow Hogan is often a popular character to include. He's Yusei's friend and his presence can add more depth to the story. Another one could be Jack Atlas. His rivalry with Yusei and his strong personality make him a great addition. Also, Akiza Izinski might be included as she has her own powers and a connection to Yusei.
Greg is the main character in this story. Given the title, we can assume he has some connection to the watch falling through the cracks. He might be the owner of the watch, or he could be in a situation where he is responsible for the watch and the accident that befalls it. Without more of the story, it's hard to say exactly what kind of person he is, but he's clearly central to whatever events unfold regarding the watch.
One key moment could be when Yusei first saves Akiza from a dangerous situation. This act of heroism makes Akiza see Yusei in a new light. Another might be when they have a heart - to - heart conversation under the stars, sharing their deepest secrets. This deepens their connection.