Nothing more than a drabble regarding a scene that could be Arrietty's future. Noctiluca, by the way, can be used as a term to identify fireflies.
"Spiller. Spiller, come look at this."
The wild Borrower boy awoke to Arrietty's voice whispered near his ear and a faint scent of flowers that still lingered where she had been lying next to him. Groggy and drowsy, he reached out—he was hoping to pull her back down, back to him. But he was too slow and Arrietty had already moved excitedly towards whatever she wished to show him, out of his reach, when she noticed him beginning to stir.
A little disappointed, Spiller grunted and scrambled to his feet. He reached for his bow just in case.
Now wasn't exactly the time to be feeling romantic, though, traipsing through forest when they were supposed to be on an errand for Arrietty's father. And although he sometimes (well, maybe always) worried about his companion, mostly he felt lucky that his wife's curiosity was enough that she loved his restless wandering.
"Arrietty… see something?" His voice was a little softer now than it used to be. It was still rough, but it had lost some of the gravelly sound over time.
"Yes! Yes, Spiller, you've just got to see this. Hurry though, or you'll miss it!" She was still ahead of him and out of sight, and he took note of her excitement as it drifted back in a barely constrained whisper.
"Spiller coming," his low voice rumbled. He picked up his pace a bit, still keeping every hunter's instinct on the alert.
An uncomfortable thought suddenly struck him. Had Arrietty been awake all night, looking around? The idea distressed him, and suddenly he doubted his ability to take care of her; he had sworn to Pod that she would be well looked-after. But maybe he was too used to being alone. Maybe she was too free-spirited.
Spiller recognized that the rustles of movement ahead had stopped and changed direction. He waited patiently, expecting Arrietty to return and possibly chastise him for being too careful, too slow.
Instead she caught him slightly by surprise by nearly bumping into him. He had to reach a hand out to steady the girl—maybe her stealth still wasn't as sharp as it should have been, he realized with another pang.
Wordlessly, Arrietty reached for his hand and flashed him a large, sweet grin. She pulled him forward, and it took all of his concentration to match her pace and still move in a way that was perfectly balanced and perfectly soundless.
The couple burst through an entanglement of vines and leaves into a wide grass field. Arrietty stopped abruptly, then; but her fingers still laced loosely through his. Shoulders back and hair rising, Spiller eyed the open space warily. It took Arrietty's gentle persistence to draw his attention away from searching for potential dangers to the scene she saw.
Hundreds of light were blinking in and out. Some drifted lazily on the breeze, looking like small lanterns that had escaped the confines of Human Bean houses. Others hung near the grass and patches of wildflowers, every illumination sending an explosion of emerald or pink or violet into their vision.
"There's so many," Arrietty laughed, finally disentangling her hand from his. Spiller gave a short nod and waited for her to continue, but she was uncharacteristically silent for a minute. Despite still looking delighted by the sight of the lightning bugs, her expression was a little distant.
He found himself getting a sick feeling in his stomach.
"Back before we met," she started, and Spiller averted his eyes from her face, "do you remember that there was a garden around that house? I would try to borrow some herbs and things for dinner, but I always had to watch out for that silly cat…." Here her voice might have hitched. "Maybe not," she continued. "Maybe you never got the chance to see that much of it. But sometimes at night I would go outside to the garden just to get out of the house. I used to see the fireflies and envy them for how bright they were, and how they could show the whole world that they were going wherever they wanted." Here she looked thoughtful for a moment, and then broke into a giggle. "Of course, Mother hated me sneaking about like that. She worried about everything, especially when I went off at night."
The ache of jealousy made him uneasy. Years had gone by, and yet his skin still prickled to hear memories that didn't include him. Maybe he was hopeless. But Arrietty's laughter was contagious, and soon Spiller found a smile creeping up over his own face.
He didn't really want her running off in the middle of the night either, he thought, but at least she bothered to wake him up. And now that he thought about it, he distinctly remembered her falling asleep first; in front of a smoldering, dying fire, she had buried herself in his arms and her face in his chest. The thought brought back another fierce twinge of desire to be sleeping next to her, which he shook off stubbornly.
Spiller's broad grin must have encouraged her, because Arrietty suddenly spun, arms out and white nightdress flaring to accent her fiery hair. She tumbled freely into the boy and knocked both of them into the grass, her feet kicking up and her arms around his neck. They were both looking up at the stars now, and she was chattering again in the normal lively way that she had. Once again it became hard for him to think—somehow that was always the case around her.
Contentedly, he wondered if he had better get used to it.