It proves they are safe.
In folklore, the “omen dog” (often a black dog, a spectral hound, or a stray that appears from nowhere) is a messenger. In Celtic myth, the Cù Sìth is a harbinger of death. In English lore, Black Shuck roams the coastlines predicting doom. But in modern romantic storytelling, the omen dog has a new job: www omen dog sex
Then a stray, three-legged, one-eyed black dog wandered between them during a thunderstorm. The dog didn’t growl at her curse. It licked his trembling hand. And that night, for the first time in ten years, the librarian dreamed of spring. It proves they are safe
If your love interest walks into the room and the family dog—who loves everyone—hides under the table and growls? That is not a quirk. That is the universe (via fur and fangs) screaming, Run. In English lore, Black Shuck roams the coastlines
Think of the viral meme: “If my dog doesn’t like him, I don’t either.” Now amplify that by a thousand. If the supernatural , omen-bearing, death-adjacent hound of destiny decides that your love interest is a good boy? That love interest isn't just a green flag. He’s a legend. She was a cursed librarian whose touch withered flowers. He was a retired monster hunter hiding from his past. Neither believed in love.