A casual relationship is one in which two or more people are dating, spending time together regularly, and engaging in romantic or sexual activities but there are no plans for the relationship to last. 4. Casual sex. A casual sex relationship is one in which two or more people spend time together solely to have sex. 5. 2. They're A Million Miles Away. They might be sitting next to you, but that's about where the closeness ends. "The most telling clue that the person your with is on the verge of ending your.