"You know the secret place?"
Robin's voice echoed in the hallway.
Astera turned his head. Robin's eyes sparkled in the candlelight.
"...What?"
"Follow me."
Robin started walking first. She didn't wait for an answer.
Astera hesitated for a moment, then followed. He was curious where this six-year-old was trying to take him.
The two headed into the depths of the library.
An area where people rarely came. Narrow passages continued between dusty bookshelves.
Robin stopped in front of a spiral staircase in one corner.
"Here."
The stairs led downward. It was dark.
"...Here?"
Astera asked. Robin turned her head to look at Astera.
"Yeah. Are you scared?"
"No."
Astera shook his head. The corner of Robin's mouth lifted slightly.
Robin went down first. Astera followed.
One floor.
Two floors.
Three floors.
It got darker and darker. A few candles were lit on the walls, but the light was weak.
"How much further?"
Astera asked. Robin's answer came from the darkness.
"Almost there."
The stairs ended. Beyond a narrow corridor, a small space was visible.
Sunlight slanted in through a window. Dust sparkled in the light.
"Here."
Robin entered the space. Some books were stacked on the floor. You could tell at a glance this was a place Robin came often.
"It's the quietest place. Nobody comes here."
Robin sat on the floor. Astera sat next to her. Sunlight coming through the window lit up both children.
"If you study here, nobody bothers you."
A moment of silence passed.
Astera looked around. It was an old place but clean. You could see signs someone had carefully maintained it.
"Have you been coming here alone? This whole time?"
Astera asked. Robin's shoulders flinched.
"...Yeah."
Her voice got small.
"Up there... there's too many people."
"I see."
Astera nodded. He didn't ask more.
After a moment, Astera spoke again.
"Can I come too? From now on?"
Robin looked at Astera. Her big eyes blinked. She seemed to hesitate for a moment, then nodded.
"...Yeah."
The two sat side by side and opened their books. Sunlight lit up the pages.
Rustle.
Only the sound of turning pages echoed quietly.
After a while, Robin murmured softly.
"My mom was here too. When she was little."
Astera looked up.
"Your mom?"
"Yeah. She was a scholar."
Robin's voice trembled. She continued while looking down at her book.
"She left on an expedition four years ago. She hasn't come back yet."
Four years ago.
Astera recalled his own memories too.
"...My father too, six years ago."
Robin turned her head. Their eyes met.
"...We're similar."
"Yeah."
Silence fell again. But this time it wasn't heavy. It was actually comfortable.
'This child is like me.'
"Do you want to come here tomorrow too?"
Robin's voice came. Astera turned his head to look at Robin. Expectation lingered on her small face.
Astera nodded.
"...Yeah."
* * *
From that day on, the two met there every day.
At first they each read their own books, but gradually conversation increased.
One day Astera asked.
"Do you remember your mom's face?"
Robin stopped turning a page. She thought for a moment, then shook her head.
"...Not really."
"Really?"
Astera asked. Robin nodded and continued.
"She left when I was two. The scholars just tell me 'Professor Olvia was an amazing person.'"
"I see."
Astera also lowered his gaze and said quietly.
"I only remember my father's back. For my mother, just her smell and the feeling of her hands."
Robin looked at Astera. A look that understood each other without words.
After a moment of silence, Robin spoke.
"Are you coming here tomorrow too?"
"Of course."
Astera answered with a smile. A small smile spread across Robin's face too.
* * *
The seasons changed.
Half a year had passed since arriving at Ohara. Astera turned thirteen, and Robin turned seven.
During that time, he regularly sent letters to his sister through News Coo. Professor Clover began teaching ancient texts in earnest, and the two took classes together.
"This character is sky."
Clover drew a character on the chalkboard. The sound of chalk scraping the board rang out.
"Who can read it?"
"Sky."
Robin answered immediately. Astera was still looking at the character.
Clover nodded with a satisfied expression.
"Robin is fast."
Clover looked at Astera.
"Astera, what about you?"
"...Why did this character come to mean sky?"
Clover's eyes sparkled. A smile spread through his beard.
"Good question."
After class, on the stairs toward the secret place, Robin said to Astera.
"I envy you."
"Why?"
Astera asked. Robin answered as she went down the stairs.
"You look for reasons. I just memorize."
Astera shook his head.
"But you're faster than me."
"Still."
Robin turned around and smiled.
They knew they were each good at different things. It was cooperation, not competition.
* * *
A year passed.
Snow fell on Ohara. Since Astera was from the South Blue, it was his first time seeing snow.
He stood by the window looking at the snow. Robin stood next to him too.
"Amazing, right?"
Robin asked. Astera nodded and looked outside.
"Yeah."
White things fell from the sky and covered the ground. A scene he'd only seen in books.
Robin murmured while looking outside.
"I wonder if Mom saw things like this. I heard the expedition went to islands with snow too."
Astera looked at Robin. Robin's expression looked a little sad.
"Will Mom come back?"
A small voice. Robin's hand gripped the windowsill tight.
Astera answered without certainty.
"She'll come back. Because she's your mom."
Robin looked at Astera. Her eyes were red.
"You'll stay with me until then, right?"
"Of course."
Astera nodded. Relief crossed Robin's face.
The snow kept falling. White snowflakes tapped the window.
* * *
One day, Professor Clover called Astera aside.
It was the professor's study. A room packed full of books. Clover sat at his desk.
"Sit."
Astera sat in a chair. Clover opened an old book.
"It's time to tell you about the D Clan."
Astera's eyes widened. His heart started racing.
'Finally.'
"D is related to the name of a great kingdom from 800 years ago."
Clover's voice lowered.
"History erased by the World Government. In an era called the Void Century, there were those who bore the name D."
"What did they do?"
Astera leaned forward and asked. Clover shook his head.
"Nobody knows. Because the World Government erased everything."
Clover looked straight at Astera. His gaze was serious.
"But one thing is certain. The World Government still fears the D even 800 years later."
"Why?"
Astera asked. Clover closed the book and answered.
"That's what we're searching for."
Clover hesitated for a moment, then spoke. Complex emotions crossed his wrinkled face.
"Your father was searching for the same thing."
Astera clenched his fists.
What his father was searching for.
'I've gotten one step closer.'
* * *
Night.
Astera told Robin about Clover's story. In the secret place on the third basement floor.
"The D Clan... the Void Century..."
Robin murmured. Her eyes sparkled.
"I think it connects to the Poneglyphs. The professor said the Poneglyphs contain erased history."
The two looked at each other.
"Can we find it? The Void Century."
Robin asked. Astera thought for a moment, then spoke.
"It'll probably take a long time, but..."
He continued.
"I want to find it. Because it's what my father was looking for, what Professor Clover is researching, and what you want to read."
Robin held out her hand. It was a small hand.
"Let's find it together. Someday we'll reveal the truth."
Astera took Robin's hand.
"Promise."
"Promise."
Stars shone in the night sky. It was the small vow of two children.
* * *
Two years were passing.
Astera turned fourteen, and Robin turned eight.
For some reason, no reply letters were coming from his sister. Thinking she must be busy with something, he continued learning at Ohara.
One day Robin asked Astera.
"Have you heard the rumor that there's something at the very bottom of the Tree of Knowledge?"
"...The very bottom?"
Astera asked. Robin nodded and lowered her voice.
"Yeah. It's an old rumor among the scholars. Nobody goes down there."
Robin's eyes sparkled.
"Want to go check it out? Just curious."
Astera thought for a moment.
'Professor Clover didn't forbid it. We just never went because we weren't interested.'
"...Okay. When?"
"Tomorrow night. When everyone's asleep."
Robin brought her finger to her lips and whispered. Astera nodded.
* * *
The next night.
The two children stood in front of the stairs leading to the very bottom, holding torches. It was a much deeper place than the secret place on the third basement floor.
"Are we really going?"
Astera asked. Robin nodded.
"Yeah."
Robin stepped onto the stairs first. Astera followed down.
The stairs were endlessly deep.
One floor.
Two floors.
Three floors.
The air became cold and damp. The torchlight illuminated the walls. Shadows wavered.
"How much further down do we have to go?"
Astera asked. Robin's answer came from ahead.
"I don't know. This is my first time."
The two kept going down. Only footsteps echoed in the darkness.
Tap.
Tap.
Tap.
That's when Robin stopped.
"There."
She held up the torch to light ahead. The stairs were ending. Beyond it, something was visible.
A wide space.
And in the middle of it...