The "Ultra-Low Fertility" as a Capitalist Bank Run

South Korea's total fertility rate (TFR), plummeting to unprecedented levels of 0.6–0.7, has perplexed demographers,sociologists, and mainstream economists worldwide. Standard neoclassical frameworks, most notably Gary Becker’s"Quantity-Quality Trade-off" hypothesis, conceptualize declining fertility as an optimal microeconomic consumer choiceunder constrained income. This paper presents a fundamental critique of Becker’s framework, arguing that it suffers fromstructural superficiality by ignoring systemic platform dynamics and mandatory input inflation. We propose an alternativemacro-financial framework: re-conceptualizing ultra-low fertility as a Systemic Social Bank Run on the capitalistplatform state. Drawing on Diamond–Dybvig liquidity crisis models, we demonstrate that young cohorts are not merelyoptimizing consumption; rather, they are executing a collective asset withdrawal (withholding reproductive capital) inresponse to the perceived bankruptcy of the social platform’s future return on investment (ROI). Using econometric proxymapping of real estate price-to-income ratios (PIR), private education expenditure, youth employment volatility, andpension solvency indicators, we operationalize this hypothesis and discuss why conventional micro-incentive welfaresubsidies fail to halt the systemic crisis.