You Think I’m Useless? After I Left, the Saintess Fell to Darkness

“Lynn, you’re a useless tr*sh who can’t even cast a fireball. You don’t deserve to stay in the Hero’s party. Get lost and go die in the demon realm!” After three years in another world, Lynn, who secretly possesses the mind of a top-tier scientist, was mercilessly cast out by the arrogant hero. Everyone assumed he would be torn apart by monsters. That is, until he encountered a soft, white-haired demon lord girl on the verge of starving to death in the middle of a snowstorm. Lynn sighed, picked up a wrench and a test tube, and said, “If humanity won’t have me, then I’ll bring an industrial revolution to the demon race.” Detoxified potatoes, mana-powered greenhouses, refined fertilizers, steam-powered mechs, magic Gatling guns… As the demon race became well-fed and well-equipped—and began rolling out tanks to conquer the continent—the human side fell into complete chaos. The once pure and flawless saintess succumbed to darkness and defected in the dead of night, sneaking into Lynn’s lab in revealing attire. “Lynn… a world of light without you is unbearable. Let me become your personal witch…” The aloof and prideful sword saint, the noble elven mage—one after another, they all switched sides and rushed to the Demon King’s castle, even fighting among themselves just to win Lynn over. Staring at his now-empty party and the one-meter-caliber magic cannon aimed ahead, the arrogant hero completely broke down. “How the hell are we supposed to fight this?!”