Two days had passed since the night a star disappeared. イスラ could still recall that moment with perfect clarity. On the eastern side of the horizon, a first-magnitude star had simply winked out. No sound. No warning. Beneath the hands gripping the wheel, the compass needle had trembled faintly. Since then, the Greyfeather had continued westward across the Calm Inner Sea, and now lay moored at a dock extending from an unnamed island. ──── The morning light was white, spreading across the water's surface like a caress. The small island facing the shallows had no name on any map. An old navigation log noted it only as a place where the tides ran gentle and fresh water could be drawn from rocky outcrops. The Greyfeather's hull bore a small scar and tidal marks—the carved seals used to activate the techniques of tide and wind manipulation—that had been etched there for over a century. In the morning light, they glowed faintly. イスラ was rolling a water barrel alone. Sweat traced down their neck. The barrel was heavier than expected, and each time the wheels caught in the gaps between the dock planks, they had to wrench it free with force. Their jet-black hair clung to their forehead with perspiration. Then something fluttered down at their feet. A scrap of parchment, carried on the wind. Stained edges. Dry ink marks. イスラ stopped the barrel and picked it up, eyes scanning the contents. ——Observation data for the vanished star, written in precise numerals. Even at the Needle House of Harbors in Nebrina—the shop that dealt in old sea chart copies—イスラ had never seen data this detailed. Observation times by location. The coordinates of the disappeared star. The compass deviation. In the margins, a small note correlating the data with the declining precision of tidal mark techniques. The moment イスラ's brow furrowed, trying to parse the numbers, they felt tension gather at the scar between their eyebrows. Behind them, a door opened quietly. A small stone structure. A crumbling cottage built beside the dock. イスラ hadn't thought anyone was inside. Turning around, they saw a young man in a white academic coat. He appeared to be in his late twenties. Smooth silver-grey hair was loosely bound at the back, swaying slightly in the morning breeze. His features were refined, but what struck イスラ most was his eyes—the right one a pale blue, the left one silver. Different colors in each eye. Combined with skin that was unnaturally white and clear, there was something about him that felt distant from reality. A gentle smile played at his lips. A natural, soft smile. But that smile was not directed at イスラ. The young man's gaze was fixed straight on the Greyfeather's hull. "Forgive me. The wind carried it away," His voice was quiet and measured. イスラ held out the paper. "Is this yours?" "Thank you," The young man accepted it, but still didn't pull his gaze from the ship. イスラ turned slightly, as if to confirm what he was looking at. The Greyfeather's hull. The old tidal marks. "...Something?" "No. I was simply observing something rather rare," The young man finally turned toward イスラ. His smile remained unchanged. Calm. Unbroken. He introduced himself. カイル・レウィス. A scholar of natural history, he said. ──── "The tidal marks on this ship follow a carving style from over a hundred years ago." カイル approached the Greyfeather's side and ran his fingertip across the wooden hull. His finger traced the outline of the pattern, barely touching the surface. イスラ watched silently. He was right. Dario from the Iron Wedge Workshop had said the same thing. "The marks are old. Don't know where you got it, but it's been at least a hundred years," he'd said. It was accurate knowledge. But what struck イスラ more was something else. "A natural historian is well-versed in tidal mark styles?" "It falls within the scope of maritime natural history. The technical history of tidal mark techniques is the very history of navigation in this world," A smooth answer. Perhaps not a lie. But イスラ narrowed their eyes. カイル unfolded a large, ancient star chart from his leather satchel. Fine script and star positions were marked on parchment, its edges slightly yellowed. "The star eclipse—the phenomenon that began three years ago, where stars in the night sky vanish one by one—causes compasses to go haywire in the open ocean. This star chart contains tidal current data corrected for the disappeared stars. It has higher precision than current sea maps," イスラ reached out and fixed the edge with their fingertip. Reading the numbers. Indeed—the tidal records around the Red Needle Reef were recorded at nearly three times the density of their own materials. (This is usable.) The practical calculation came first. Before emotion, the math moved. Three hundred kilometers west of Nebrina lay the Red Needle Reef—a treacherous passage where red coral formations rich in iron jutted near the surface, easily tearing through a ship's hull. Precise tidal data was essential to cross it. "Would you allow me to travel with you?" カイル spoke gently. His smile unchanged. "I'm researching phantom islands. If you're heading west, I thought our directions would align," イスラ said nothing for a moment. "Are you with the Verdant Beacon Academy?" The Verdant Beacon Academy—the highest academic institution of the Verna Republic, known for theoretical research in tidal mark techniques and maritime natural history—イスラ had named it as a test. There was a beat before カイル's response. "...No, I conduct research from an independent position. I don't hold any title from the academy," A beat. Just a short pause. A person who usually responded immediately to being addressed—why only there? Something clicked inside イスラ. Not sharp enough to call wariness. But definitely, a switch had flipped. Answers that were too smooth were sometimes prepared answers. "...Very well. You're welcome to board," The practical value of the star chart outweighed the doubt. For now, that was enough. ──── The problem was the luggage. The cargo カイル brought out from the cottage was three times what イスラ had anticipated. Instruments for astronomical observation. Several thick bound journals. A complete set of cooking tools. And four large burlap sacks. イスラ surveyed the cargo stacked on the dock and mentally calculated the Greyfeather's draft. Adding excess weight to the hull risked scraping bottom in the shallows of the Red Needle Reef. "What are in these burlap sacks?" "Dried beans. I calculated them as a nutritional source for forty days. Beans are nearly a complete nutrition, and for extended voyages——" "Leave half of them behind," "But from a nutritional calculation standpoint——" "From a draft standpoint, I'd prefer you left all of them. Half is a compromise," カイル's expression wavered for a moment. His smile stopped, then returned. With a reluctant air, he carried two of the burlap sacks back to the cottage. Watching his retreating figure, イスラ felt their own mouth relax slightly. (I didn't expect a natural historian to talk about beans.) The cargo problem was solved. But something more important had been settled—at least, how イスラ would position themselves in relation to this young man had been decided. ──── As the sun tilted and the sky turned red, the Greyfeather began running across the Calm Inner Sea once more. After sunset, カイル settled himself on the deck and spread out the old star chart. Lantern light illuminated the parchment. カイル ran a quill across the paper while alternating his gaze between the night sky and the chart. He seemed to be recording the positions of disappeared stars. The quiet of his work dissolved into the night of the deck. イスラ stood before the wheel, adjusting the compass. They confirmed the needle's tremor with their fingertips while observing カイル's work from the corner of their eye. His movements were natural. No hesitation. Efficient. The movements of a genuine researcher, perhaps. But that beat wouldn't leave イスラ's mind. イスラ released the compass and slowly walked toward カイル. They stopped at an angle where they could look down at the star chart. "Where did you gather this data?" "I collected it while traveling to various observation posts. Over five years," カイル moved his finger across the star chart. He traced several marks indicating observation points, then slowly moved his finger toward a single location. "The estimated position of the phantom island is here. When you overlay the current sea chart data with the distribution of disappeared stars——" イスラ naturally extended their own finger. The point where カイル's finger had stopped. At the edge of the Star-Devouring Sea, just before entering the dark depths. イスラ moved their finger toward that location. The two fingers were about to overlap at nearly the same moment——when カイル quietly withdrew his hand. The motion was natural. He tilted his body slightly, creating distance. Whether intentional or unconscious, イスラ couldn't tell. His smile remained unchanged. His expression revealed nothing. イスラ's finger remained alone on the star chart. (What was that?) A faint ripple spread through イスラ's chest. They thought it was wariness. They tried to judge it that way. But the more they tried to settle on that name, the more it felt imprecise. At the angle of looking down at the star chart, the distance between them wasn't great. カイル's profile was there in the lantern light. Silver-grey hair flowed along his neck. イスラ realized their awareness had shifted from the star chart to カイル's profile and pulled their gaze back to the chart. (Focus. Look at the chart.) They scolded themselves internally. This young man had a mystery in that beat. There was no reason to trust him. So why—— "What do you want to do once you find the phantom island, イスラ?" カイル spoke quietly. His gaze remained on the chart. イスラ paused for a moment. "I'm searching for something I've lost," "Specifically?" "I don't know. But I know it's there," カイル said nothing. Only the hand holding the quill stopped for a moment. ──── The night deepened. While カイル was absorbed in his calculations, a wind swept across the deck. The hem of カイル's coat fluttered up. イスラ's gaze drifted toward it casually——and stopped. From the satchel's opening, something was visible for an instant. A black leather journal. On its cover, a gold relief. An emblem depicting a burning lighthouse. ——The emblem of the Verdant Beacon Academy. The wind ceased, and the coat hem fell back. カイル continued his calculations, seemingly unaware. His silver-grey hair swayed faintly in the night breeze. イスラ walked toward the wheel. Behind them, the lantern light cast カイル's shadow across the deck. An independent position. No title from the academy. Then what was that journal? Why carry what appeared to be internal materials from the Verdant Beacon Academy? イスラ decided not to voice that question tonight. They gripped the wheel with both hands. The night Calm Inner Sea was peaceful, and wave sounds struck the hull in steady rhythm. イスラ quietly weighed the reasons to trust against the reasons not to. A beat of mystery. The Verdant Beacon Academy emblem. Words too smooth. Yet the star chart was genuine. The tidal data for crossing the Red Needle Reef was truly usable. (I don't need to judge yet.) They placed their palm against the Greyfeather's tidal marks. Through the embroidered glove on their left wrist, the sensation of wood returned to them. And a faint warmth——the inexplicable warmth this ship possessed——transmitted through their palm. No flashback came tonight. No white light. No sensation of someone's hand. Only a quiet night, a scholar writing on a star chart, and a night sky with one star missing. In イスラ's chest, only a nameless ripple remained. Was it wariness, or something else——the answer had not yet been found. The Greyfeather sailed west across the Calm Inner Sea. Three hundred kilometers to t