"Okay," said Usopp, taking out paper and a pen and placing the pen onto the paper. "Sanji's really tired during day, but apparently not at night . . ." he wrote this down. "His skin is pretty damn pale . . ." he wrote this down as well. "What else?"
"His hand brushed mine the other day," Robin said. "It felt unusually cold."
"Cold skin . . . okay, anything else?"
"Nothing comes to mind at the moment."
"Hm . . . Sanji's sleeping in the kitchen right now, right?"
"Yes."
"So . . . how about we go up there and take a closer look?" Usopp stood up.
"Fine," Robin agreed. "But I'll examine him from the outside of the kitchen. I wouldn't want him to wake up and find us standing over him."
They headed up to the kitchen. Once outside, Robin closed her eyes and formed an X with her arms. If you were to look inside, you would see a hand sprout on the ground near where the sleeping cook lied, and an eye on the wall next to it.
First, Robin gently touched Sanji's hand. The cook twitched, but didn't wake. She opened one eye and said "He's definitely colder than he should be. But other than that, and the fact that he's asleep, there isn't anything else unusual about him. But . . ."
"Yeah?" Usopp asked, pen at the ready.
"Wait." Concentrating, she sprouted a chain of arms, placing an eye on the end of the last one. With this strange method, she scanned the kitchen. After a moment she said "That's odd. There's no sign of him having eaten recently."
Usopp frowned. "He's not eating? Come to think of it . . . I don't think he's been using the bathroom, either. He hasn't left the kitchen in a long time—except at night, apparently."
"It's interesting," Robin said after vanishing the arms and eyes inside the kitchen. "Sleeping during the day, combined with moving about at night and apparently eating at night (if at all), would imply that he's nocturnal."
"What? But . . ." Usopp said. "How?"
"I'm not sure," Robin said calmly, though an idea was forming in her mind. "It's not exactly a normal thing for someone to become nocturnal when previously they were diurnal, correct?"
"Definitely not," Usopp muttered. "So . . . he's probably nocturnal . . ." he said as he wrote this down.
"I have an idea," Robin said, "but I'll need to test something first. Sanji does keep a small hand mirror in the kitchen, yes?"
"Yeah," Usopp said. "Why, what—"
Robin shut her eyes and ignored him, crossing her arms again and this time using her powers to open up the drawers in the kitchen until she found the mirror. She quietly took it out and held it up in such a way that it reflected the place where Sanji should have shown up.
But the mirror reflected only the floor beneath him.
Usopp saw her tense. "What's wrong? What are you doing?"
Before answering, Robin quietly returned the mirror to its proper place, shut the drawer, and got rid of the hands. She opened her eyes and looked at Usopp.
"What's wrong?" Usopp repeated.
"I held up the mirror," Robin said in a troubled voice, "and it showed the place where Sanji was . . ."
"And . . . ?" prompted Usopp.
"And it reflected everything that was supposed to be there," she replied. "Everything . . . except Sanji himself."
Usopp dropped the notepad, which landed on the deck with a thump. "H-He didn't show up in the mirror?"
"Correct."
Usopp was starting to piece it together. "Nocturnal . . . pale skin . . . not eating . . . not showing up in a mirror . . . not going outside in the day . . ."
It all clicked.
"H-He . . . S-Sanji's a v—"
Robin covered his mouth. "Shh," she scolded. "What if someone were to hear you? Let's go back to the aquarium room."
Usopp nodded, unable to do much else with his mouth covered.
Once they had reached the aquarium, Usopp started screaming. Robin slapped him. He blinked. "S-Sorry . . ."
"It's quite all right. Now," she continued, "all signs point to him being a vampire—don't you agree?"
He nodded nervously.
"But," she continued, "We don't have definite proof yet. We haven't actually seen him feed; it may in fact be only a strange illness, as Chopper claims. Tonight, after dinner, I can follow him into town—if he indeed goes—and find out what he does."
"That sounds good . . ." Usopp mumbled. "But, uh, Robin?"
"Yes?"
"Please, please don't say 'feed'. It's really creepy."
"Would you prefer I say 'drink'?" she suggested lightly.
"'s not much better," Usopp grumbled.