Humanity's Existence Depends on Love Gambling with Another World's Princess

Lumis, the daughter of the Great Demon Lord, arrives at a prestigious all-girls boarding school with a single, deceptively simple goal: to experience the thrill of romantic love for the first time. Disguised as an ordinary transfer student, she enrolls in the class taught by Kazuki, the institution's sole male instructor—a position that already makes him an anomaly among the sea of young women. For Kazuki, navigating the daily chaos of hormonal teenagers is challenging enough, but his world turns upside down when he accidentally overhears a chilling ultimatum: the Demon Lord has sworn to annihilate the entire planet if his precious daughter ever sheds a single tear. Suddenly, Kazuki's mundane teaching career becomes a high-stakes tightrope walk where every lesson, every interaction, and every errant word could spell the end of humanity. One wrong move, one unintentional slight that clouds Lumis's bright expression, and Earth faces immediate annihilation. Yet the true torture lies in Lumis herself—an earnest and endearing girl whose genuine pursuit of romance leaves Kazuki perpetually caught between paralyzing fear and an unexpected, burgeoning attraction. With the weight of the world literally resting on his ability to keep a demon princess smiling, this ultimate heart-pounding romantic comedy unfolds, where love is not just a gamble—it is the very condition for human survival.