Well, 'ex' is probably your former partner. They might be watching your stories out of curiosity. Maybe they still care about what's going on in your life, or they could be just nosy.
Well, a frequent theme is the development of their relationship. It often starts with some sort of attraction or connection and then grows into a deeper bond. There's also the theme of power dynamics, as the alpa and omega designations imply certain power and social roles that are explored in how they interact with each other. Additionally, some stories may have a theme of redemption or self - discovery within the context of their relationship.
Yes, there are quite a few. You can start by looking on popular fanfiction websites like Archive of Our Own. Just search for 'alpa yami x omega yugi' and you'll likely find a range of stories. Some might focus on their relationship development, while others could explore different scenarios within the context of this pairing.
Well, 'ex' is probably your former partner. Maybe they still have an interest in your life and are eager to see what you're up to, so they are always first to watch your stories.