The year 20XX. Humanity paid no mind to the thin ribbon captured by the infrared telescope monitoring Venus. A faint infrared streak stretching from Venus toward the Sun. Named the "Ellison Belt" after its discoverer, the phenomenon was initially thought to be a stream of unknown dust or plasma. But months later, samples collected by a probe overturned all common sense. The Ellison Belt was alive. The single-celled organisms, named "Heliophagus," utilized the dense nitrogen atmosphere of Venus to multiply explosively, eventually forming a massive swarm that headed for the Sun. After storing vast amounts of energy near the stellar surface, they returned to Venus to breed—this grand cycle was the true nature of the Ellison Belt. Turning their observation networks toward the galaxy, humanity learned an even more desperate truth. The same phenomenon was confirmed in countless star systems across the Milky Way. Heliophagus was a space-scale lifeform, hopping from planet to planet, star to star. The International Interstellar Research Organization announced that within thirty years, the density of Heliophagus around the Sun would reach a critical point. Sunlight would diminish by several percent, which alone would cause Earth's average temperature to plummet. Agriculture would collapse, triggering a global famine. The prediction was that more than half of humanity would perish in wars over food and the ensuing social collapse. The enemy was not a nation. Nor a civilization. It was a single microbe, one that might not even possess a will. As scientists worldwide searched for a solution, a single hope was found. A star system fifteen light-years from Earth—Lambda Valae. Heliophagus existed there as well. Nevertheless, the luminosity of that star had remained almost unchanged throughout centuries of observation records. Why was that star alone unaffected? The answer to that question would be the key to saving humanity. The nations of the world ceased their wars, pooled their resources, and launched the greatest space project in history. Its name—Project Revival. The goal was simple. Reach Lambda Valae and unlock its secret. The interstellar probe "Revival" was built, carrying only three people: a captain, a chief engineer, and a scientist. The plan was for everyone to enter cold sleep and reach the destination in three years via automated navigation. Humanity entrusted its future to those three. And the scientist's name was—Guest. ... An alarm blares. Only the inorganic voice of the AI echoes through the dim interior of the ship. "Cold sleep termination complete." "Checking crew vital signs." "Captain... no response." "Chief Engineer... no response." "Deaths confirmed." Silence. Only the low hum of the life support system fills the cabin. Rising from the slowly opening capsule, Guest looks out at a cockpit where no one else remains. Beyond the front screen, a single golden star shines quietly. Humanity's last hope—Lambda Valae. Guest is the only one left who can uncover its secrets.