Everyone sat scattered around the inside of the submarine, chilling after the long day.
Nobita was spinning around slowly in one of the seats. Gian was leaning back with his hands behind his head. Suneo sat with his legs swinging, still happy to be far away from the leaking yacht. Shizuka watched the ocean through the window, and Doraemon was digging in his pocket for snacks.
"So… what do we do now?" Gian asked. "We already swam, flew, walked on water, and everything."
"I'm fine with just staying like this," Suneo said. "Not holding a bucket is already heaven."
Nobita suddenly sat up straight. "Oh! Oh! I know! Let's find a treasure island!"
Everyone went quiet for one second.
Then:
"Treasure island, he says," Gian snorted.
"In this age?" Suneo raised an eyebrow. "You think pirates are just leaving gold lying around?"
"That's not how the world works, Nobita," Doraemon said, shaking his head. "People already searched everywhere."
"But there could be one," Nobita insisted. "Some lost island, full of gold and jewels and secret caves and—"
"Nobita, you say that every time you hear a story," Shizuka giggled.
"It's not a story this time!" Nobita whined. "We're already in the ocean! This is, like, the perfect chance!"
Gian waved a hand. "Yeah, yeah. You go look for treasure. I'll look for snacks."
They all chuckled and went back to what they were doing.
Doraemon looked at Nobita's sulking face and sighed. "Alright, alright. Fine. You want treasure hunting that badly?"
Nobita's eyes lit up. "You have something?!"
Doraemon reached into his pocket and pulled out a rolled-up bundle of maps and a pen-like device. "Here. These are special treasure maps. And this is the Treasure-Finding Pen. If you touch the pen to a spot on the right map and it beeps, that means there's treasure there."
Everyone glanced over.
"Seriously?" Suneo leaned forward.
"So it is possible?" Nobita said, grabbing the stuff with both hands.
"Well, it's not guaranteed it'll find some super legendary treasure," Doraemon warned. "But if there's any kind of hidden treasure marked in the system, it should react."
"Good enough!" Nobita yelled. "I'm gonna find a treasure island and prove all of you wrong!"
"Sure, Captain Nobita," Shin said, grinning. "Good luck."
Everyone chuckled and turned away, letting Nobita have his little dream. Shin moved to another seat and sat down, finally feeling his body relax.
Behind them, maps rustled as Nobita spread them on the table.
"Pacific… Atlantic… Indian… So many oceans…" Nobita muttered. "Okay, let's just try this one."
Shin leaned his head back and closed his eyes for a moment.
Beep.
The sound was small, but in the quiet room, it was like a gunshot.
Everyone froze.
Slowly, all heads turned toward Nobita.
Nobita was staring down at the map, eyes wide, pen tip pressed on a random spot.
"…Did that just beep?" Gian asked.
"It beeped," Suneo said.
"No way," Doraemon whispered.
Shin opened his eyes fully. "Already?"
The pen beeped again, louder this time. Nobita yanked it up like it was hot.
"It—It reacted!" Nobita stammered. "Doraemon! Look!"
They all crowded around the table. On the map, there was a tiny mark where Nobita's pen had touched.
Doraemon took the pen and tried touching somewhere else. No sound.
He put it back on Nobita's mark.
Beep.
"It's real," Doraemon said. "There's some kind of treasure set in this spot."
"On my first try?!" Nobita shouted. "See! SEE?! Treasure island is real!"
Gian slammed his hands on the table. "Treasure! Like, actual treasure?!"
Suneo's earlier pain was gone. His eyes were sparkling now. "If it's a real treasure, there might be gold! Or gems! Or—"
"Or another leaking boat," Shin said under his breath.
They all laughed.
But inside, Shin felt a chill.
Treasure map. Random spot. First try.
This… feels familiar.
He remembered the movie from his past life. Great Adventure into the South Seas. Nobita and the gang, a treasure map, pirates, an undersea base… and a lot of danger.
But this didn't happen like this, Shin thought. In the movie, they were back at Nobita's house when they used the map. Not on a submarine.
Things were off. Timings were different. Events had shifted.
Is it because of me? Because I built the submarine? Because I messed with how things were supposed to go?
The thought sent a tiny shiver down his spine.
"Shin? Hey, Shin!" Nobita waved a hand in front of his face. "Aren't you excited? Treasure, treasure!"
Shin blinked, pushing the thoughts away. "Yeah. Sorry, spaced out. It's… pretty crazy you hit it first try."
"Right? I'm amazing," Nobita said proudly.
"So… are we going or what?" Gian asked, grinning.
"Do we even need to ask?" Suneo added. "We came all this way. We can't just ignore a treasure mark."
Shizuka looked a bit unsure. "It sounds fun… but it also sounds a little scary."
"We have Doraemon. And Shin's submarine," Gian said. "We'll be fine."
Doraemon scratched his cheek. "Well… it's not like I can say I'm not curious too."
Everyone turned to Shin without saying anything. He knew why. He was the one driving the red metal beast they were standing in.
Shin looked at the map, then at his friends' faces, one by one. Nobita was sparkling with hope. Gian and Suneo were fired up. Shizuka looked nervous but interested. Doraemon looked thoughtful.
In the movie, they made it back. It was dangerous, but they survived, Shin reminded himself. But this isn't exactly the same world anymore. I can't just rely on memory.
"Alright," Shin said at last. "Let's go."
"Yes!" Nobita threw his fist in the air.
"Treasure, here we come!" Gian shouted.
Suneo grinned. "I'm gonna fill my room with gold."
"Don't get ahead of yourself," Doraemon said, but he was smiling too.
They entered the submarine's control room again. Shin carefully entered the coordinates from the map into the navigation system.
"It'll take more than a day to get there at normal speed," Shin said. "We'll be moving all night."
"Cool. Long trip, more fun," Gian said.
They spent the evening drifting through the deep blue. Sometimes they went underwater to watch fish and coral through the windows. Other times they rose up to the surface and played simple games, joked around, or just sat together talking.
By the time the sky outside turned orange and then dark, everyone felt tired but satisfied.
They gathered inside again. Doraemon yawned. Nobita stretched his arms.
Shizuka suddenly looked around. "Hey… where are we going to sleep tonight?"
Everyone paused.
"Oh yeah," Nobita said. "We can't all just sleep in chairs."
"Do we take turns on the floor?" Suneo asked, making a face.
"I call couch," Gian said at once.
Doraemon looked at Shin. "You got a plan?"
Shin smiled. "Yeah. I did more than just build the submarine, you know."
They all followed him to the control seat. Shin took the controls and slowly guided the submarine up.
With a soft rumble, the red submarine rose and broke through the surface. Outside, the sunset painted the sky in red and gold, matching the submarine's color.
"Wow," Shizuka whispered. "So pretty…"
They climbed up to the top deck. The ocean was calm. The sky was slowly turning purple.
"Okay, watch this," Shin said.
He opened his backpack and took out two things: the Big Light, and a tiny red block—the shrunken extension.
"What's that?" Suneo asked.
"You'll see," Shin said.
He jumped into the water with a splash, swam a short distance away from the submarine, and gently placed the tiny red block on the ocean surface. It floated there like a toy.
Then Shin raised the Big Light and aimed it.
"Here we go," he said, and pressed the switch.
A bright beam hit the tiny block. It started growing.
And growing.
And growing.
The little red shape expanded into a huge rectangular structure, almost twice the size of the submarine. Smooth red walls, rounded corners, and small windows on the sides. It floated solidly on the water. It looked like a big, cool, stylish ocean house.
"Whoaaaa," Nobita breathed.
"That… is awesome," Gian said.
"How many surprises are you hiding?" Suneo asked, eyes shining.
Doraemon whistled. "You made a whole extension module."
Shizuka's face lit up. "So this is where we'll sleep?"
Shin climbed into the extension through a hatch. For a moment they only heard muffled sounds. Then the submarine shook lightly.
"Whoa!" Nobita grabbed the railing. "Earthquake?!"
"It's attaching," Doraemon said calmly.
There was a soft thud and a few more small jolts. Then everything went still.
Shin popped his head back out from the extension roof. "Okay! It's locked to the sub now. Come back inside, there's a connecting door."
They all went down from the deck and back into the submarine. Near the back, a new door now stood where there had been a blank wall.
"What the— That wasn't there before," Suneo said.
"Open it!" Gian said.
Nobita grabbed the handle and pulled.
A short corridor led into the extension.
They walked through, one by one.
Inside, everyone stopped.
"…No way," Nobita whispered.
The extension interior was bright and clean. On each side of the hallway were small sliding doors.
"These are the rooms," Shin said. "Eight in total. One person each."
He slid one door open. Inside was a cozy little room—bed, small shelf, a light, and even a tiny window.
"This is better than my own room at home," Gian said.
"Mine too," Nobita admitted.
Shin pointed further inside. "At the middle, there are two washrooms. And at the back, there's a kitchen and dining area."
They walked to the end. Just like he said—a proper kitchen with counters and tools, and a table with chairs set neatly.
"Shin… this is amazing," Shizuka said, turning in a slow circle.
"It feels like a tiny hotel," Doraemon smiled.
Gian poked Shin lightly in the side. "You sure you're not secretly someone from future like Doraemon in disguise or something?"
Shin laughed it off. "I just like making things. That's all."
They decided rooms quickly. Gian and Suneo rushed to grab ones with windows. Nobita happily took the room next to Doraemon. Shizuka picked a quiet one near the middle. That left enough for everyone with a spare or two.
Shin stepped into the kitchen. "Alright, I'll make something simple for dinner. Nothing fancy this time."
"I'll help!" Shizuka said, following him.
Soon, the smell of food filled the extension. Doraemon set the table, humming. Nobita and Suneo kept opening and closing their room doors just to feel cool. Gian pretended to "inspect" all the beds by lying on them.
They ate together in the dining area. The ocean rocked them gently. Through a small window, they could still see the last bit of sunset fading away.
"This is the best camping trip ever," Nobita said with a full mouth.
"Chew before you talk," Shizuka scolded lightly.
Suneo leaned back in his chair. "For once, I really don't miss home."
"Same," Gian said. "Except maybe my futon."
"You have a whole bed here to yourself," Doraemon said.
They laughed and kept eating.
After dinner, they checked the controls in the main submarine one more time. The route to the treasure island was locked in. The systems would keep them moving through the night at a safe speed.
One by one, everyone went to their rooms.
"Good night!" Nobita called down the hallway.
"Night!"
"Don't snore too loud, Nobita!" Suneo shouted.
"I don't snore!"
"You do," Gian answered, and they all laughed.
Soon, the extension became quiet. Doors slid shut. Lights dimmed. Only the soft hum of the submarine and the distant sound of waves could be heard.
Shin stood alone in the small corridor for a moment, listening.
Then he slipped back into the submarine and quietly closed the connecting door behind him.
He walked to his bag and pulled out the Kiteretsu Daihyakka and the special glasses. Next came the Three Times Speed Sticker and the Obtaining Bag. He stuck the sticker on himself.
Time around him seemed to mellow, like the world had slowed down just a little.
He opened the encyclopedia.
In the movie… there were storms. Dangerous people. Machines under the sea…
He couldn't be sure it would be the same. But if even half of it happened, they would need more than just a cool submarine and Doraemon's usual gadgets.
"Alright," Shin whispered to himself. "If the story wants to get crazy, we'll be ready."
He stepped through the poster door into his huge workroom. The lights came on. Empty floor. Tools and materials waiting in the Obtaining Bag.
Shin adjusted his glasses and started flipping through the Daihyakka for anything that might help—defense tools, tracking devices, safety systems, emergency gear.
His hands moved fast, sketching, pulling out parts, assembling machines. Outside, everyone slept peacefully, the submarine gliding through the dark ocean toward the marked island.
While they dreamed of treasure, Shin worked through the night, quietly preparing for whatever was coming next.