The Engine’s Heartbeat

Yuuto woke up to the circle of sunlight crawling across his face. It was squeezed through the thick glass of the porthole window, looking more like a pale moon than the sun. He rubbed his eyes, yawned and stretched his arms, his joins popping in the silence. 

Back home, morning was loud. The toaster’s ding. The rattle of commuter train. The frantic shuffle of his parent getting ready for work. Cram school to attend. Church pews to sit in. He never got to oversleep like this. Here, the only clock was the tide. Now, every day was a holiday, a Sunday afternoon that refused to end. 

He slipped on his indoor slippers. The floor was concrete and cold here, a sharp contrast to the plush carpets in his old life. He peeked into Kousuke's room. The man was still sleeping in the heap of blanket; his rhythmic snoring echoed through the small space.

Boredom was a heavy thing. Yuuto began his exploration of the lighthouse. He climbed the spiral stairs, his small hands trailing on the cold iron railing. He ventured toward the forbidden zones—the engine room and the observation deck. He could see the mainland from the high windows, through the wall of gray fog like a fantasy place. What was his hometown a few days ago now became a place he couldn't reach.

He went down to the second floor to find Kousuke still asleep. Desperate for something to do, Yuuto slipped into his plastic sandals and stepped out into the air.

The sky was clear and bright blue, and the sun was shining, yet it couldn't pierce through the dark seawater. As he wandered through the shore, he saw it. 

It was small, nestled in a pool of oily black water near the tide line. “Never go near the water,” Kousuke’s voice rang in his head. “It’s not for swimming.”

Yuuto didn't swim. He just leaned. Then he poked the thing with the stick he found yesterday. 

It had been a fish, once. Now, it was a lump of disfigured flesh covered in a substance that looked like undigested oil. It was bloated, its scales peeling away to reveal a sickly, translucent white beneath. 

It looked like a fish that had been reimagined by a nightmare.

Yuuto loved the sea. He loved the beach trips with his parents, the aquarium tour with his class, and the sea creatures. He knew his fish. He even had an encyclopedia of them. But no matter how hard he recalled his memory, he could not identify this thing. 

Like he could not recognize his own parents face. 

“Yuuto! Get away from there!”

Kousuke’s voice was a thunderclap. The man scrambled down the rocky path, his boots skidding. He grabbed Yuuto’s shoulders, spinning him around with a frantic, wide-eyed intensity. “Didn’t I tell you? No touching. No going near the water.”

It took Yuuto a while to recover. He stared at Kousuke using the stick to push the creature back to the wave, careful not to let the water touching him. When the sea swallowed the lump, Kousuke exhaled a long, shaky breath.

“Let's go inside,” Kousuke said, his voice softening but still strained. “Breakfast. We need to eat.”

Yuuto nodded and followed the man back inside the lighthouse, before taking a final glance to the sea. He wondered if there were more of those “wrong” creatures drifting beneath the surface.

***

Breakfast was a shared can of peaches and a dry, chalky food bar that tasted like compressed sawdust. Yuuto was glad it wasn't tuna. He didn't think he could look at a fish for a long time.

“I have to do my daily maintenance now. Kousuke said, gathering the tin trash. “You stay in the common room. Play with your dinosaurs or something.”

“Can I watch you work?” Yuuto asked. His voice was small; his eyes fixed on Kousuke with a pleading intensity that the man couldn't ignore. The boy looked terrified of the silence between the walls.

Kousuke hesitated, then sighed. “Sure. I guess a tour guide wouldn't hurt.”

What followed was a slow trek through the lighthouse's iron guts. Kousuke explained the radio—the heavy, silent box that emitted nothing but white noise and static. He showed Yuuto the underground well, pulling a sample of water into a glass vial.

“We test this every day,” Kousuke explained, his face illuminated by a flashlight. “If the radiation seeps through the rock, the water will change. If that happens, we stop drinking. Understand?”

Yuuto nodded, though the "why" felt too big for his head.

By midday, the technical jargon of water filters and barometric pressure had worn Yuuto out. He wandered back to the shore, keeping a safe distance from the water this time. He used his stick to carve shapes into the sand—not castles, but dolphins. He wanted to remember what a real dolphin looked like before the oily sea erased the memory.

Day 4: 

Visual perimeter check conducted at 8:00. Found a biological specimen on the North Shore. Disfigured, possibly a deep-sea mutation brought up by the blast's thermal shift. Pushed it back to avoid contamination.

Air quality: Metallic tang is stronger today. 

Radiation levels within 'acceptable' yellow parameters. 

Yuuto is... restless. He followed me during the generator check today. He asks too many questions about the water. I told him it’s just physics, but I don’t think he believes me. He spent the afternoon drawing dolphins in the sand. I didn't have the heart to tell him the dolphins are likely all dead.

***

Night fell, and the cold became a physical weight. To cheer the boy up, Kousuke took him to the very top—the lantern room.

The diesel generator was alive, a deafening, rhythmic thrum-thrum-thrum that vibrated through the soles of their feet. It was the only "heartbeat" on the island. Inside the glass housing, the great lens began to turn. 

Yuuto's eyes widened in awe as he saw the blindingly white light cut through the foggy air like a sword. For a second, he could see the distant, hazy glimmer of the mainland. It looked like a star fallen to earth.

However, the light cannot shine through the black sea. It absorbed everything, lives, even light couldn't escape it. 

“Check the waves,” Kousuke said, handing the boy a pair of heavy binoculars.

The boy scanned through the whole area, excited that he could see the waves clearly. Floating logs. Clumps of gray foam. And the swirling patterns of the current.

Then, his breath hitched.

Just at the edge of the light’s reach, something shimmered. A flash of silver-blue scales, a long, powerful tail that broke the surface and slapped down with a heavy, wet thud. It was graceful. It was huge. It was not a fish, it was something bigger, like a mermaid out of a fairy tale.

“Did you see that?” Yuuto gasped, thrusting the binoculars at Kousuke. “Kou-san! A mermaid! I saw a tail!” 

Kousuke took the lenses and scanned the area. He saw nothing but the rhythmic churn of the black tide. “Probably just a large piece of debris, Yuuto. Or a trick of the light.”

“It wasn't debris,” Yuuto whispered.

As if in response, the wind changed. The roar of the generator seemed to fade, and through the glass, a faint, vibrating melody drifted up from the dark. It was louder tonight, clearer.

“Do you think mermaids exist?” Yuuto asked. He was humming, his small body swaying slightly to the rhythm of the waves.

“Not really,” Kousuke said, his hand resting on the boy’s shoulder. “But the sea is vast, so anything could exist down there, even if it is beyond human comprehension…”

“So, you think…” Yuuto’s gaze drifted to the distant mainland. “Will people become mermaids if they die in the sea?” 

“I don't know.” Kousuke answered honestly. “But if that was the case, they would be really lonely down there…”

“No one to talk to. Just the singing.” Yuuto whispered. 

The sea gave them no answers, just the blows of wind and the distant lullaby. Kousuke looked at the black water and realized he didn't have a single word of comfort to give. He just tightened his grip on Yuuto’s shoulder as the light swept over the abyss, revealing nothing but the darkness it couldn't pierce.