The remainder of this work is organized as follows: in Sec. II, we first delineate an open quantum system model describing a molecular aggregate embedded in solvent and an optical cavity environment. Following that, we provide a brief introduction to the HEOM+MPS/TT method and the observables of interest. Subsequently, in Sec. III, we present the simulation details and discuss results for a series of models with increasing complexity: a single molecule inside and outside the cavity, as well as two molecules inside the cavity. Finally, a summary of the underlying reaction mechanisms and prospects for future works are provided in Sec. IV.