Lin En, a veteran Warhammer fan and galgame player, dies after clicking a suspicious pop-up ad and awakens in the Warhammer 40,000 universe. He is Lin En Ke'er Wa Na, a twenty-two-year-old low-level Tax Inspector on the Necromunda Hive World's Seventh District, an impoverished underhive dweller whose parents died in an Ork assault. Almost immediately, a shoddy galgame-style dating system binds to him, presenting three interaction targets: a Khorne-corrupted Guard Captain, a Tech Priestess of the Machine Cult, and a Tyranid Hive Warrior.

With danger ratings stacked against him, Lin En chooses the only viable option—the silent, emotionless Tyranid unit, whom he names Lena. Severely injured, starving, and severed from the Hive Mind, Lena initially views him as edible biomass at -55 Affection. Now Lin En must navigate the grim darkness of the underhive, evade Adeptus Arbites patrols, and somehow romance a xenos warrior before the Hive Mind reclaims her or the galaxy's countless horrors kill them both.