One-shot, based on kind of a strange theory I came up with. Slight, weird Puzzleshipping at the end.

Yami raised his eyes from the cards in his hand, watching his other half curiously.

"Yugi, what are you doing?"

Yugi had come to the spirit earlier that night to ask if he wanted to look through their deck. He said that he'd just bought some new cards that he wanted to fit in somewhere, but he was too tired to look at it tonight, and he wanted Yami's advice on what to replace, anyway. Yami had agreed, honored that Yugi would value his input on something as personal as his deck, but he was starting to wonder if the boy was really as tired as he claimed. Yugi hadn't been doing much resting since Yami had taken over his body. Instead, he was… well, Yami wasn't really sure.

Emerging from the Puzzle in spectral form, Yugi had spent the first few minutes staring at his hands, passing them in and out of objects with almost morbid curiosity. Then he stood up, jumped up and down a little, and started walking, running his hands over and through everything in sight. Once he reached a certain distance away from the Puzzle, his body faded even further; frowning, he walked backwards and returned to normal. Eventually he stopped walking and started floating, rising upwards until his head stuck through the ceiling. At this point, Yami realized that he could no longer even pretend to focus on cards. As Yugi floated back down to earth, Yami repeated his question.

"What are you doing?"

"Experimenting," Yugi said absently, as if that explained everything. His feet were melting into the floor now as he went downwards this time, falling into the room beneath them.

Yami waited for him to reappear before asking his next question. "Why?"

"Because."

"That's not much of an answer," Yami observed as Yugi continued floating around the room, trying to push objects over with his finger. "And that's not going to work."

"Yeah, I'm noticing," Yugi said with a frown. He had stopped in front of a Dark Magician figurine sitting on his desk. "I mean, I can touch it like this, see?" He pressed his finger against the object.

"I know."

"And I can go through it, like this, but I can't make it move!" He waved his hand through the toy in mild frustration.

"I know," Yami repeated. "I am well aware of that form's limitations."

Yugi blushed. "Sorry, I guess you would be. I just—I'm not."

Yami watched him for a moment longer as he fidgeted, embarrassed, and floated away again. There was a hidden motive behind these actions, he realized suddenly, something more than idle curiosity. He just hadn't asked the right question yet—or at least, not in a way that Yugi would answer.

He decided to try a different tactic.

"Come here," Yami said, putting down the deck and patting the bed next to him. "I have something to show you."

Surprised, Yugi hesitated, and then floated over, perching on the bed beside him.

"What is it?"

"You are sitting on the bed," Yami said, and Yugi's brow creased.

"Yeah, you called me over—"

"Rather than falling through it," he clarified. "You are capable of doing both, yet you automatically chose to sit on it, trusting that you would not fall through."

"Yeah," Yugi said slowly. "But I know I'm capable of doing both…"

"When you first started moving around," Yami went on, "you walked, even though gravity has no real hold on you. It wasn't until you started… experimenting that you tried to float."

Yugi scratched his head. "I don't know. I saw you doing it once, so I thought—"

"Exactly!" Yami interrupted him. "You've seen me do it! Would it have occurred to you to try it if you hadn't seen me doing it?"

"I…" Yugi tilted his head in thought. "I don't know. I might have thought about it eventually. I mean, being a spirit is kind of like being a ghost, right? And ghosts can fly."

"A ghost?" Yami frowned. "I remind you of those floating white sheets children wear on… Halween?"

"What?" Yugi asked. "Oh, Halloween! Oh, no, not exactly. A ghost is just a person who has died but their soul is still trapped on Earth. Most people don't believe in them, though. I'm not sure how that whole sheet thing started…"

"I see," Yami lied.

"But that's not the point, because I think I get what you're saying," Yugi said. "I'm limited by my expectations in this form, aren't I? So if I didn't think I could float, on some level at least, then I couldn't. For the most part, I do whatever comes naturally to me."

"Exactly," Yami said with a grin. "You experience the world as you perceive it to be. There are limits, of course, boundaries that can't be crossed. For example, no matter how much you believe it should be so, nothing you do has any effect on the physical world around you. You cannot move even the tiniest of objects. See how, even though you're sitting on the bed, there is no indent in the covers to show your presence?"

"But how far does that go, exactly?" Yugi wondered. "I mean—okay, take this piece of carpet over here," he said, jumping up and running over to the corner of the room to touch the ground. "It feels a bit cold like the rest of the carpet, right? Because I was expecting it to feel cold, because the room felt cold to me earlier. But—but it's right next to the heater vent, which I didn't even notice before! So it should be…" Yugi closed his eyes, concentrating. "Yes! It feels warm now. Yami, this is so weird!"

Yami stared at him, speechless. Some measure of his shock must have filtered through their bond, because Yugi turned his head to look at him.

"What's wrong?"

"I…" Yami cleared his throat. "You can… feel temperatures?"

"Um, yeah?" Yugi said. "I mean, kind of. I'm not feeling the real temperature, obviously, if it can change like that, but I feel whatever I'm expecting to—" He stopped, eyes widening. "You didn't know."

"I assumed it wasn't possible," Yami admitted. "I have not been truly alive for many years. The ability to feel just didn't make sense."

"But… but you can feel textures right?" Yugi asked desperately. "I mean, you can feel the difference between this and this, right?" He put one hand on the carpet and another on the wall as demonstration.

The look in Yami's eyes said it all. Yugi dropped his hands, horrified.

"You can't," he said. "So that's what it's like."

"What what's like?" Yami asked, frowning when Yugi didn't respond. "Yugi, I know that there was something more than curiosity driving your actions tonight. You had a purpose behind these experiments. What was it?"

"Oh…" Yugi's face heated up. Looking anywhere but Yami, he said quietly, "This'll sound stupid, but I wanted to know… wanted to make sure that your… your existence wasn't—isn't—"

All at once, it clicked in Yami's mind.

"You wanted to know how it felt to be me." His tone turned incredulous. "You wanted to pity me in a more informed context?"

"What?" Yugi asked, almost panicked. "No! That's an awful way to put it."

"But true."

"No," Yugi repeated, firmly this time. "It's not true. I don't want to pity you, Yami. I just wanted to know what it was like so I could understand you, maybe identify with you. I wanted to make sure it wasn't so bad, but—" he ran a hand through his hair. "—But you're telling me that aside from when you're in my body, you've never felt anything? At all?"

"No," Yami said slowly. "No, I have always felt one thing."

Standing up and walking across the room to where Yugi was, he knelt down and placed a hand on his face. Wide-eyed, Yugi stared up at him.

"You feel… me?" he asked, and Yami nodded.

"I have always felt you."

Yugi stayed there for a moment in thought, unconsciously bringing his hand up over Yami's. Then a look of determination flashed across his eyes.

"Switch me," he said.

Quirking a puzzled eyebrow, Yami acquiesced, allowing Yugi control of the body and taking the transparent form of a spirit.

"You feel this?" Yugi asked, grabbing Yami's hand.

Yami nodded.

"Okay…" Yugi guided his hand to the carpet. "Now feel this."

"Yugi, you know I can't," he started, but Yugi interrupted him.

"Yes you can! I felt it before, so you can feel it, too. Just try."

His large eyes were so pleading that Yami found he had no choice. Closing his eyes, he concentrated, pressing his hand against the carpet.

"It's warm," Yugi said in his ear. "It's soft, but a little rough. Can you feel it?"

"I…" Yami opened his eyes in wonder. "I can."

The feeling was incredible, as sensation slowly trickled up his hand. The carpet was warm—Yami dragged his hand across it. As though this one action had opened up a floodgate, other sensations started pouring in. The floor beneath him, which before been simply existed, suddenly felt more solid, more real. His knees sunk into the plush carpet. He shivered a little as the cold air of the room finally hit him, moving unconsciously closer to the vent. And… Yugi's hand…

"You're warm," Yami said, pulling Yugi's hand closer and placing it against his cheek.

"You're cold," Yugi whispered. "I thought you could already feel me?"

"Not like this." No, never like this. His touch was almost electrifying in a way that made Yami feel both content and energized. It was all he could do to keep himself from running his hands down Yugi's pale body, to drink it all in, the electric presence of Yugi…

No. He reigned himself in, his elation dying down as he realized something.

"You know this is all an illusion," he said. "I'm not feeling the world as it really is. I'm only feeling it as I believe it to be."

"Then believe that it's good," Yugi insisted. "There's so much hard reality in the world that you already have to deal with. Would it really be so bad, to allow yourself this one illusion?"

Would it? Yami wondered, pulling Yugi further down into his embrace. Surprised, Yugi allowed it, no doubt thinking it a consequence of Yami's newfound sense of feeling, his tenuous connection to Yami's mind unable to pick up on the desires this ability to feel had awakened, of heavy breaths and moans, bodies meeting, colliding in heat and sweat and lightning…

Yami looked down at Yugi, and wondered if he already lived in a world of illusions.

Yugi shivered, and wondered why.