One day they had to die.
It was a simple fact that every human or alien had to die at a certain age, whether it be from an illness or their bodies growing too weak to function. But Starfire had a very hard time facing up to that fact whenever her eyes met Robin's, and their fingers entwined slowly. The moments were too perfect for her to think about the end.
These thoughts were rushing through her head on a particularly quiet day at the tower. Robin was inching his face closer to her own, his eyes closed and mask discarded to the floor when they had first fallen into this position on the bed. She could feel the magnetic pull of Robin's lips, and wanted desperately to allow herself to let go and be drawn into her boyfriend's body. But she couldn't. Not with the whirlpool of thoughts raging around in her mind at the thought of having to leave planet Earth, to leave the Universe, and never return.
Robin froze, eyes still shut and body wavering in the gap between their faces. He waited for a few moments, then hesitantly opened his eyes. He was met with the sight of Starfire in a hunched up position against the wall, refusing to meet his eyes.
"Star?" He asked, inching closer. "Did I do something wrong?" He reached his hand out and was relieved that she didn't object to it resting on her leg.
"I just- Robin. I'm so sorry to ruin our moment, but I am worrying about later. What will we do when we are old? How shall we protect the planet when we are... Gone?" She gazed at him with wide eyes, uncertainty and slight fear etched into them like an open book. Robin sighed.
"Star, there are other heroes who can take over our work. We don't have to be heroes forever. We're the Teen Titans, remember? We'll keep saving Earth until we're ready to stop. Then we can live together like any normal couple and leave the bad guys to the next generation. That's how it'll always go, Star. Forever." He lifted his hand from her leg and rested it against her pale cheek.
"Just because we're gone, it doesn't mean the Earth is doomed. Superheroes are immortal in that way. We just keep coming." She smiled slightly at his words, but still felt troubled.
"But Robin, I do not think I can deal with the- the- the death," Starfire choked, eyes watering slightly. Robin moved closer, arms steadily winding their way around her.
"Hey Star, Star! Don't cry, it's okay. Just don't think about the future; live in the now. And remember: Immortal. It doesn't matter whether it means us or our work, we're immortal."
And it had more than one meaning, Starfire could see. Superheroes were immortal, yes. But so was her relationship with Robin. While they themselves weren't immortal separately, together they could keep going forever.