That afternoon, the sun hung like a copper gong, and the air beat time like a slow drum.

Day three of special training had a steady rhythm, and Professor F’s project slid cleanly into Lesson 3 like a blade into silk. The morning’s island run warmed them up like coals under a kettle; the afternoon would uncork the real brew.

“Lesson Three: underwater exploration!” His voice rang like a bell over water. “You’ve got to adapt to strange terrain. An enemy won’t stroll onto your favorite stage for a fair duel.”

Ling Yi glanced at Yekase for help, like a sparrow peeking toward a willow branch.

Yekase lounged on the bench by the training ground, a quiet cat in the shade. Zhang Wendao sat on her lap with the calm of a stone in a stream.

“‘Dew’ has underwater combat capability,” Yekase said, fingers tapping like rain on tin. “Honestly, I added it back then for the color scheme and the name.”

[Doctor, you’re my hero!] The mechanical voice chimed like a wind-up music box.

“You don’t have to emphasize that…” Her smile twitched like a ripple in a tea cup.

Guilt pricked like a thorn under the nail.

“You’re trusted by that person,” someone murmured, the words falling like a leaf.

“Mm.” The assent was soft, like dusk settling.

The Dragon God Shark raised the Beast King Cube, and in single-unit mode the Dragon God’s Tail leapt from the armory roof like a silver fish, arcing into the sea. A white flash, like a gull’s wing, and she slipped into the cockpit.

She snagged Crimson Field by the collar and hauled him in like a fisherman scooping a wriggling catch.

Not to be outdone, Ling Yi produced her key. Light blossomed like dew on grass. She became “Dew” and streaked after them, a blue swallow diving.

So many fights in a single week; kids grow like bamboo after rain. Yekase sighed and kneaded Zhang Wendao in her arms like soft dough, flattening and rounding with idle cruelty.

Why was Zhang Wendao here watching with them? The question bobbed like a cork.

Because she kept insisting she was combat personnel, and she wanted a look at the fresh heroes nine years after the war. She came to “inspect” with a delicate air of hauteur, like silk raised on the wind.

But she was still a ten-year-old kid—ice-preserved nine years or not. If a face is a child’s and a voice is a child’s, then she’s a child, as clear as a winter moon.

A child’s high posture only makes you think of words like cute and precious, like a kitten attempting a lion’s roar. Yekase thought so too.

She hugged the embattled Magical Girl to her chest, fiddling with Zhang’s tiny hands like polished pebbles, kneading her cheeks and side bangs like warm mochi.

When she was truly seventeen, her little sister was twelve—an age that shoots up like saplings and grows a mind like spring thunder. The girl refused to sit on her lap anymore. A single dog of a mech nerd like her assumed she’d hold a child again only when her sister married and had one. Fate, like a prankster wind, chose now instead.

If she were a twenty-seven-year-old man, this scene would be a red line, like ink spilled across a scroll. But if a face is a young woman’s and a voice is a young woman’s, then she’s a young woman. The lantern stays bright.

A girl hugging a little girl—warm as a quilt in snow. Undeniably safe.

“So. The other members of the Twenty Second Squad—how many can you still recall?” Yekase’s eyes skimmed like a hawk. “Thirty-nine… no, forty erased lives. Check more of their pasts; we might spot a bug. That might be our breakthrough.”

Underwater training—no way to spectate, like watching fog swallow a stage. They had to keep grinding the files here.

[Thirty of them were combatants planted by Shadow Curtain International.] The robo-voice ticked like a metronome.

Yekase loaded a text-to-speech app for Zhang Wendao. Now her words flowed at a normal pace, like water down a channel.

“Ah, so they were also sniffing out hero intel… Remove logistics, and there aren’t many left!”

[Logistics had only Dr Ika.] The words dropped like iron beads.

“Uh…?”

[He’s incredible. He juggled tasks too many to count, like he had eight arms.]

Please stop with the octopus bit. The plea fell like a fan closing.

Youth, huh… Yekase’s gaze drifted to the far sky like a kite. In her memory, 2012 was a hive of bees. She found traces of Flash Energy that year and lived in the lab like a cave-dwelling fox, refining that first entire bottle of it—just a plastic mineral-water bottle, gleaming like trapped lightning.

According to Zhang Wendao, those precious memories were fake, a mirage over hot sand. Copy-pasted from another timeline where the 2012 war never happened. The thought felt like a pebble in the shoe. Yekase couldn’t tell.

But the Flash Energy in her hand was real. It hummed like a caged sun.

So in the real history, where she became Dr Ika’s good colleague three years earlier and was busy fighting aliens like a storm at sea—when, and by what chance, did she enter the gate of Flash Energy?

“…Huh?” The doubt flickered like a moth near flame.

[Found a contradiction?] The prompt chimed like a tuning fork.

“No, it’s nothing. Which heroes joined that war?” Her voice evened like a drawn bow.

“The Ten Iron Titans, Lily Gun-and-Blade, Jo & Jo, Dual-Pistols Dewitt, Magical Girl Ivaris… the list runs like a river.”

Good grief. Ten Titans turned to Seven; Gun-and-Blade to just Blade. Bodies fell like autumn leaves.

“What about the Sinister Organization?” The question cut like a sickle.

[Mostly Shadow Curtain International.] The answer was a flat stone.

“Mm… I get the picture.” The conclusion settled like dust.

No breakthrough from that angle. Heroes who died in that year-long war had their deaths blurred like smudged ink, or rewritten like a forged seal.

And thinking back—until last year, enemies who were oil and water, even heroes she didn’t know now, might have fought and bled with her in that vanished time, celebrated victories with lanterns and drums… The thought sat crooked, like a painting hung wrong.

Danganronpa? Don’t play me like that. The protest popped like a soap bubble.

“Ladies, care to tour the undersea world?” Headlights flared into Yekase’s vision like twin stars.

“—Whoa?!” The yelp hopped like a startled hare.

“No need to jump that high.” Professor F patted the hull like a loyal horse. “My Observer is on par with the Dragon God Pioneer. It flies, and it moonlights as a submarine.”

“What a deep trench…” Yekase’s gaze drifted to Professor F’s chest like a compass needle that refused to behave.

He didn’t catch her drift. “You’ve investigated it? The very deep trench nearby. Its sides are oddly regular, like a man-made edifice. I chose this site partly to explore it.”

“It’s very deep. And the shape is… pleasing.” Her words tried for innocence and failed like a cat with feathers on its mouth.

Zhang Wendao sighed, reached behind Yekase, and pinched her in the side. The grip bit like a crab claw.

“Ow ow ow—just a joke, a joke…” The pain came in chopped beats, like a stuttering wave.

Yekase surrendered, lifted Zhang off her lap, and set her aside like a delicate vase. Professor F assumed they were horsing around—which they were—and taxied his ride over, beckoning them aboard like a ferryman.

Then the plane knifed into the sea, a silver carp plunging through blue silk.

“W-whoa…” The world outside the porthole drowned in deep blue, like ink poured over glass. Yekase pressed her forehead to it and saw Ling Yi and the Dragon God’s Tail, one large, one small, two blue machines roaming a little deeper like whales on a lazy drift.

Below them ran a trench, black and fathomless, a canyon of ink stretching parallel to the Observer until it vanished into the dim like a road to the underworld.

Even Zhang Wendao grew quiet, her gaze tethered like a lantern floating downstream.

“…This is less a trench and more a piece of architecture.” The thought clicked like a key in a lock.

“You think so too,” Professor F said, pleased, like a teacher hearing the right answer.

He let the autopilot hum like a hive and stepped over. “I tried entering many times. Drop past a certain depth, and pressure spikes unnaturally, like a trap springing. I also detected faint energy signatures.”

“Ancient ruins?” Yekase’s eyes lit like coals. “If there’s an energy response, some of the machinery might still be running. Which energy?”

“Omega Ray. And Flash Energy.” The names rang like twin gongs.

“Flash—” She whipped around to stare at him, disbelief bright as lightning.

“When I didn’t know Flash Energy’s nature, I couldn’t identify the second signature. After you gave me a sample, I could. It’s Flash, clear as day.”

“I always thought Flash Energy was a modern development,” she murmured, like someone finding frost in summer.

“We already have ‘plain users’ like Qiao Feng and Qiao Shiyu,” he said. “No surviving texts doesn’t prove no one used Flash in ancient days.”

Plain users. People who run Infinite Power straight through the body, hand-cranking the engine, like Ling Yi brute-forcing Mind Energy and Flash Energy. A useful term, tucked away like a pebble charm.

Light thinned as they went deeper, half gone in a blink, like dusk in a forest. The Observer’s lamps cut cones through the murk, and the world returned in pale sheets.

They entered the trench. The walls looked like giant black tiles pressed together, layered like dragon scales, with the gaps between layers a pure dark that swallowed sight like a well.

“Lucky for us, the trench has clear, visible tiers,” Professor F said, voice steady as a keel. “We can enter the top one with our current hardware. Today’s lesson is a sea-bottom expedition.”

“Multiple floors…” Yekase pictured it like a dungeon map, a tower flipped on its head, stairways sinking instead of rising.

A novel hero might chase power and loot through ruins like a moth to fire. Yekase was a desk-jockey by creed, a builder of cannons, not a borrower of miracles—no guns, no cannons, we make our own thunder.

“Can we go in now?” Curiosity tugged like a tide.

“Any time.” His nod cut clean as a sail.

But ancient machines ran inside. Machines still breathing like buried hearts. That, she couldn’t ignore.

Yekase glanced at Zhang Wendao. The girl gave in with a tiny grimace, agreeing to watch the boat like a temple guardian. Yekase tried to ruffle her hair; Zhang smacked the hand away like a sparrow pecking. So Yekase and Professor F donned special diving suits, and a white blink took them outside like a step through moonlight.

Ling Yi, Crimson Field, and the Dragon God Shark clung to the Observer’s handholds like barnacles. Once Yekase adjusted to moving in water, the five of them swam toward the top-tier space like a school of fish finding a current.

Ling Yi drifted close and took Yekase’s hand, fingers cool as river stones.

Her voice piped through the headset, clear as a bell: “It’s dark here. Don’t let go of my hand, Doctor.”

“…Do I need you to comfort me?” Yekase muttered, pride fluttering like an anxious moth.

She wasn’t athletic compared to trained fighters, but among beginners she always found the trick first, like a key turning instinctively. One of her gifts was learning from zero; adapting to the new like reeds bowing with wind.

Among first-timers, she was always the first to look like she belonged. Once everyone caught up, she vanished into the crowd like a drop in rain.

So now, as ever, she drifted to the front like a lead lantern—

“…” A pause snagged her breath like a hook.

She glanced down without thinking. Below lay nothingness, ordinary dark like a room with the light off—at least it should have been. But—

…

[Doctor?] Ling Yi felt the hand in hers go rigid, like ice forming across a pond. She turned and saw Yekase stiff from limb to limb, trembling, frozen in place like a deer under a thunderclap.

“Ah, this is…” The words came slow, like syrup.

This was the fabled…

[Thalassophobia. The deep-sea kind?] The diagnosis landed like a pebble sinking into endless blue.