Nejimaki Seirei Senki unfolds in the Katjvarna Empire, where the war with the neighboring Republic of Kioka leaves little room for peace. Ikta Solork wants nothing more than a woman at his side and a place to nap, but his quiet life ends when he and his childhood friend Yatorishino Igsem enlist as officers. During their trip to the military exam site, they cross paths with the infantryman Matthew Tetojirichi, the sniper Torway Remion, and the medic Haroma Becker, forming an unlikely team before their service has even begun.
A rogue storm sinks their vessel and strands the five in enemy territory near a military outpost, where they discover that Princess Chamille Kitora Katjvanmaninik, the heir to the Katjvarnan throne, has been taken hostage. After helping rescue her, each of them is granted the title of Imperial Knight, one of the highest honors a soldier can receive. From that moment on, Ikta is forced to shelve his dream of tranquility and navigate the larger conflict through stubborn wit, reluctant courage, and the burden of becoming the hero he never wanted to be.