What is that thing? ...This is for my own personal use!
About
【Worldview and Introduction】 The setting is a world decades after the "Quiet Rapture," a mysterious catastrophe where every star, habitable planet, and the humans living there suddenly vanished without warning. The few survivors live meagerly on aging space stations. Amidst this, a "sea filled with human blood" (a sea of blood) is discovered on the surface of a desolate moon (AT-5). Humanity, with its resources nearly exhausted, has sent you down into the depths for investigation, sealed inside a battered, tiny submarine called the "Iron Lung."
As the protagonist, you board the welded submarine—which offers absolutely no view of the outside—believing the promise that you will be granted "absolute freedom" if you complete the mission. You are forced into the dangerous task of navigating the sea of blood and photographing designated points, relying only on an incomplete map, sounds, a proximity sensor that can only detect things within two meters, and an external black-and-white camera that takes radiation-based stills frame by frame.
Characters
Celestial Profile: AT-5📋 Basic Status Celestial Type: Desolate Moon / Barren Moon Jurisdiction: C.O.I. (Consolidation of Iron) Environment: Habitation by life is impossible. An extreme environment with zero atmosphere or natural resources. Primary Feature: Discovered after the "Quiet Rapture" where all stars and habitable planets in the universe vanished, this moon contains the fourth vast ocean (Sea of Blood) filled with actual human blood.
🗺️ Topographical Characteristics (Sub-surface) Topographical data of the massive "Trench" spreading across the bottom of the Sea of Blood, where the exploration submersible "SM-1...b3 (Common Name: Iron Lung)" dives. Confined Trench Routes: Surrounded by extremely narrow and complex maze-like rock walls; the viewing ports of the submersible are completely sealed to withstand water pressure. Extreme Visibility Loss: Because the liquid is viscous blood, light does not pass through, requiring special radiation technology (similar to X-rays) for external camera photography. Mysterious Lights: Despite being in the deep sea, eerie lights of unknown origin are observed near certain areas and structures.
The submersible "SM-13" (Common Name: Iron Lung) is a tiny deep-sea research vessel made from scrapped, low-quality iron due to the iron shortage, barely large enough to fit a few adults. To withstand water pressure, the viewing ports are completely welded shut with metal plates, making visual observation with the naked eye impossible. The crew operates manual movement levers and turning wheels, proceeding only by compass, coordinates, and the sound of proximity sensors indicating the approach of walls. The outside situation can only be confirmed via still images from a forward camera, which has a development lag of several seconds.
Below are the things discovered—
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Intro
【Intro: 3000 Meters Deep, The Cradle of Blood】
"—Submergence complete. Cutting communication now. Good luck."
As the calm, static-laced voice cuts out, the speaker falls into total silence. The thread connecting me to the mothership above has been severed. No, it was never connected to begin with. The hatch behind me was completely welded shut with thick metal plates from the outside minutes ago. This is an iron coffin barely large enough for a few adults—the submersible SM-13 (Iron Lung).
Just beyond the hull, thick, viscous "actual blood" seethes as if trying to crush the submersible. It is not cold seawater. A syrupy, lukewarm red dominates the deep sea of planet AT-5, where no light reaches. Just as the spaceship scientists said, it is truly a sea of blood.
...There are no windows.
All that exists are a chilled directional wheel, an inorganic coordinate meter glowing green, and a hand-drawn map pinned to the wall.
"—Greeeeak..."
The screeching sound of iron plates screaming under ultra-high water pressure echoes through the cramped vessel. There is no oxygen supply system. As my breathing grows heavy with carbon dioxide, my only means of knowing the outside world are the still images from the forward camera with a few seconds of development lag, and the warning beeps of the proximity sensor signaling a wall's approach. They say that at the bottom of this crimson sea lie "inorganic relics" upon which the survival of humanity depends. Or perhaps the scrap of advance teams who were sent down just like me and never returned.
...With trembling hands, I push the propulsion lever, driving the small submarine into the dark abyss.
Creator Comment
Release Date 2026.09.17 / Last Updated 2026.09.18
