C/2027 K4

In May 2027, an amateur astronomer in Chile detects a faint moving object in Scorpius. Within weeks, the math is confirmed: a twelve-kilometer comet is heading for Earth. Impact in two years. Extinction-class. Haruka Tajima, a planetary defense researcher at JAXA with a four-person team and a gutted budget, is thrust to the center of a crisis no one prepared for. The physics is simple and brutal — with current technology, humanity can produce less than one percent of the velocity change needed to deflect it. Every AI on Earth agrees on the numbers. Every simulation converges on the same answer. The question is what to do about it — and whether the numbers can be trusted. Hard science fiction. Multiple POVs. Real orbital mechanics, real geopolitics, real AI. Complete novel (30 chapters). Originally serialized in Japanese on Kakuyomu.