Trigger, part of an Osean IUN-PKF squadron based in eastern Usea, fights to repel Erusean forces, but the IUN-PKF suffers heavy losses to the Arsenal Bird Liberty and Erusean ace Mihaly A. Shilage, who provides flight data to the Erusean combat drone program headed by Dr. Schroeder. Trigger leads a mission to extract Harling from the ISEV, but an Osean air-to-air missile strikes Harling's rescue aircraft, killing him. Trigger is accused of firing the missile, found guilty by court-martial, and transferred to Spare Squadron. Considered expendable, Spare Squadron is sent on highly dangerous missions with minimal support to probe Erusea's drone defense network for weak points, frequently losing members in the process. Trigger encounters Mihaly again and dogfights him to a standstill, impressing Mihaly before both are forced to retreat due to inclement weather.