Aerosol effects on sea fog microphysics are nonmonotonic with aerosol concentration, and complex aerosol-sea fog interactions leave substantial uncertainty in microphysical responses. Five sea fog events observed over the East China Sea during March–May 2025 are analyzed with the aerosol-cloud interaction index (ACI) and cloud-aerosol mass mixing ratio (MCr). Positive ACI time fraction generally decreases with fog duration. MCr ranges from 2.17 to 2.93. The MCr-ACI transition range is 2.50–2.63, and 2.63 is selected as an empirical grouping threshold. Under liquid water content (LWC) constraints, ACI<sub>re</sub> at high-MCr range increases from 0.02 to 0.14 with LWC, consistent with a progressively stronger Twomey effect in droplet-size reduction. At low-MCr, ACI<sub>re</sub> changes from -0.09 and -0.03 at low and intermediate LWC to 0.21 at high-LWC, indicating that the droplet-size response can change direction with LWC. Fog droplet size spectra show that, in the high-MCr range, the response of the small-droplet mode to increased aerosol loading strengthens with LWC. Under high-LWC, the small-droplet modal peak for high aerosol loading at low-MCr is about four times the corresponding high-MCr value. This pattern exhibits pronounced small-droplet accumulation and relatively constrained subsequent growth. This difference indicates MCr = 2.63 can distinguish relatively complete and constrained activation-growth microphysical states. The autoconversion threshold function (T) response further indicates that aerosol effects on droplet coalescence also depend on the MCr-LWC state. These results show that jointly considering MCr-LWC better distinguishes the direction and strength of aerosol effects on sea fog microphysics.