We have outlined a comprehensive approach to investigate the unique responsive gas adsorption process of NGA using atomistic simulations, establishing a method to understand and predict adsorption in flexible materials. Our approach uses grand canonical Monte Carlo moves combined with MD trajectories to create an ab initio osmotic potential surface for methane adsorption on DUT-49, capturing both the effects of gas pressure and changes in cell volume. Roaming this surface using either equilibrium or kinetic trajectories produces very different isotherms. Only by considering a kinetic pathway that accounts for osmotic potential barriers are the salient features of the complex adsorption process produced, namely a NGA step and hysteresis. Subsequently, we used this model to understand the effects of temperature, demonstrating the previously poorly understood nonmonotonic trend of NGA magnitude with temperature. This trend results from the evolution of both the difference in osmotic potential and barriers between the two phases, which crucially requires a detailed description of the osmotic potential surface. The presented methodology enables ab initio prediction of NGA and permits investigation of similar counterintuitive adsorption processes. This is an important step towards predicting the evolution of conformational energy landscapes of flexible porous materials upon guest adsorption. In particular, this new insight into the barriers present in responsive adsorption processes is of utmost importance for the intended application of these materials in kinetic selectivity and recognition. Many separation process are emphasized for flexible porous materials, but hysteresis is rarely addressed and poorly understood. Hysteresis is important for both delivery and separation as it determines the energy for regeneration, and this approach highlights how desorption accesses an entirely different pathway than adsorption. Clearly, flexible systems can wander beyond equilibrium, and only by mapping the complete energy surface can we truly understand these unique adsorption phenomena and pave the way for new adsorbent technologies.