Osmotically driven release has been widely studied in responsive microcapsule systems; however, most conventional approaches rely on osmolytes encapsulated inside the core, resulting in abrupt release and poor controllability. Here, we propose a hypertonic-actuated strategy in which asymmetric dual-core microcapsules fabricated via a W/O/W microfluidic platform undergo buckling and rupture under hypertonic conditions. The capsules possess an ultra-thin shell region (<1 μm) independent of aspect ratio. Under hypertonic conditions, water efflux through the semipermeable shell generates compressive stress, inducing localized buckling and rupture at the ultra-thin region. Compared with symmetric single-core capsules, the dual-core architecture enables reproducible rupture and release under hypertonic compression. This actuation exhibits a threshold response with a critical osmolality of ~1000 mOsm kg⁻¹, and the release behavior is governed by shell stiffness.