Bubbles are falling. From above. No—that's not right. Light piercing through the water's surface is tangling itself in the particles of foam, raining down in glimmers. Forty-five meters deep. Kirishima Gen simply stared upward. This was the waters off Oosebana Cape. Beyond the cliff at the southern tip of Naruse Peninsula. A drop-off where the seabed plunges more than eighty meters in a single breath from the surface. A frightening sea that only advanced divers approach. But in this moment, it wasn't frightening at all. Sunlight, passing through water, becomes granular. Countless points of light, like particles, slant downward. They dance gently, swaying in time with the undulating surface above. Gen's eyes blurred slightly. Tears formed inside his mask. He hadn't noticed it himself. He simply thought: it's beautiful. That something this beautiful existed in this world—at twenty-six years old, Gen was learning it for the first time. A presence beside him. Takeuchi, his senior diver. With the regulator still in his mouth, Takeuchi was gazing upward in the same way. When their eyes met, Takeuchi made the OK hand signal with one hand. Okay. You alright? Gen returned the signal. They began ascending slowly toward the surface. Gen checked the numbers on his dive computer. He observed the decompression stop time. No rushing. There were rules in the sea. Those who couldn't follow the rules died. When they climbed onto land, removed their masks, and wiped the salt water from their faces, Takeuchi said: "[gentle]You're a man the sea has chosen." His tone was joking. But his eyes weren't smiling. Gen couldn't say anything. He simply nodded. He still remembers that day clearly. The particles of light. The undulating surface. Takeuchi's voice. --- Darkness. The same cape. The same waters. But there is no light. Takeuchi's body is ascending. Fast. Too fast. Gen reached out his hand. His fingertips grazed Takeuchi's fin. Just barely. A little more and he could have grabbed it. But he couldn't reach. Bubbles are erupting from Takeuchi's body. The regulator torn from his mouth, bubbles pouring out in massive quantities. Emergency ascent. Emergency ascent means death. Nitrogen dissolved in the blood becomes gas bubbles. Decompression sickness. What professional divers fear most. Gen gave chase. But he couldn't catch up. The surface draws near. Light returns. But Takeuchi's body, floating in that light, no longer moved. --- Fluorescent light is nothing like the light underwater. It's white, hard, shadows sharp and distinct. Gen opened his eyes. He looked at the ceiling. A concrete ceiling. The stained ceiling of an old warehouse. Not a dream. The usual thing. Thirty-eight-year-old Kirishima Gen stood up from the folding chair and cracked his neck. This was Sub-Zero's base. Eight minutes' walk from Minatosaki Harbor, in the back streets of a residential area. A former fish-processing warehouse. Concrete box, forty years old. On the walls: copies of certification documents and several underwater photographs. That was all the decoration. A place Gen rented for thirty thousand yen a month. Where twelve members gathered. The headquarters of "Izu Club Sub-Zero." The name came from "the resolve to dive even when water temperature drops below zero." Gen had come up with it five years ago. Some people had laughed, saying it was too cool for its own good, but Gen was serious. The notebook PC screen was still glowing. Not even in sleep mode. Frozen mid-scroll on an SNS account page. Follower count: three thousand two hundred. Every posted photo: blue sky, white sand beach, smiling men and women. "Paradise Diving Club." A leisure diving club established three years ago around Minatosaki Harbor. One experience dive for twelve thousand yen, equipment rental included. Beginners welcome, casual participation. BBQ available, beach parties available. Gen scrolled through the page. He checked each photograph. Shots taken at Kagura Bay. A cove ten minutes by car from Minatosaki. White sand beach, transparent shallows. Maximum depth twelve meters. Calm waves, beginner-friendly. In the photos, young men and women were laughing. In swimwear, wearing equipment, making peace signs at the camera. Not underwater. Still above the surface. Gen stopped the mouse. He stared at one photograph. An instructor-like man was teaching a female participant how to put on a BCD. Smiling. The woman was smiling too. But the BCD's chest strap was loose. Gen could tell at a glance. It wasn't properly tightened. That was the problem. That wasn't all. There were several other small details. They might technically meet PADI standards. But "technically" was something Gen couldn't forgive. The sea doesn't forgive "technically." A loud laugh drifted through the wall. Distant. But audible. They must be having a party at Kagura Bay tonight too. On weekends, Paradise members and experience participants gathered, had BBQs, drank, made noise. The sound carried all the way to the harbor. Gen opened another window on his PC. Text was written there. A long text. The sender was listed as "Anonymous." The recipient: "Coast Gear Co., Ltd. Customer Service Desk." Coast Gear was a diving equipment manufacturer. Third largest domestic market share. They had a regional office in Shiokaze City. They were Paradise's sponsor, providing equipment. Dozens of posts tagged "Provided by Coast Gear" appeared on their SNS. Gen read through the text from the beginning. Safety management issues at Paradise Diving Club. Specific photographic evidence. Discrepancies between instructor credentials and practical experience. Equipment inspection frequency. Inadequate buddy system implementation during experience dives. All of it was true. But the sender was "Anonymous." Gen's name appeared nowhere. (This is fine.) That's what Gen thought. He had no intention of doing this openly. Doing it openly wouldn't change anything. Paradise would say "we'll improve," make some changes, then do the same thing again. What mattered was cutting the sponsor. Stopping the money flow. If Coast Gear launched an investigation, Paradise would panic. Slowly, from small things. Gen placed his mouse cursor over the send button. He didn't move it. He simply stopped there for a moment. The warehouse was quiet. The distant laughter from outside. The faint sound of waves. The harbor was close. The smell of brine seeped into this poorly ventilated warehouse. Gen unconsciously traced the scar on his left cheek with his fingertip. An old scar. He no longer remembered when he got it. But it caught his eye every time he looked in a mirror. It was always there. He thought of Takeuchi. September, seven years ago. Fifty meters deep off the cape. Emergency ascent. Decompression sickness. Officially, it was "an accident caused by personal negligence." But Gen knew. There had been signs of nitrogen narcosis. Something was off even before the dive. But Gen hadn't stopped him. He'd made the wrong judgment. The Gen who had told Takeuchi "the sea has chosen you" couldn't save Takeuchi. Every September, Gen went to Oosebana Cape. He stood at the cliff's edge with flowers and looked at the sea. That was all. He told no one. (I won't let those bastards turn the sea where he died into their playground.) Gen clicked. Send complete. The email flew. His expression didn't change. Paradise's SNS still filled the PC screen. Blue sky. White sand. Smiling faces. Three thousand two hundred followers. Multiple sponsors. A rapidly growing leisure club. Gen closed the PC. He stood up and took a black jacket from the coat hook. Dark gray, lightweight material. He put it on, laced his shoes, and locked the warehouse. Outside, the summer night air waited. Humid, the smell of brine thick. First week of August. Stars dotted the sky. Minatosaki's nights were dark. Few streetlights. But the direction of the sea seemed slightly brighter somehow. Gen walked toward the harbor. In the distance, laughter again. From the direction of Kagura Bay. Those Paradise people, probably. Happy voices. Young voices. Voices that knew nothing. Gen stopped and looked in that direction. Dark. Nothing visible. Of course. Kagura Bay was six kilometers away. It couldn't be seen. But Gen stood facing that direction for a while, unmoving. The scar on his cheek touched the night breeze. The anger wasn't large. Not the kind that burned. It was like smoldering coals. Always there. Never going out. Burning quietly, steadily. Gen began walking. Toward the harbor, alone. The sound of waves grew gradually closer. No one knew who this man was, or why he harbored such relentless obsession.