Nearly half of planet-hosting stars are binary, and this stellar multiplicity can have a dynamical influence on planet formation processes in the system. Precise stellar properties yield precise planet properties, and provide a window into planet formation and evolution in multi-star systems. However, few studies have determined both radii and masses, and thus bulk densities, for planets in multi-star systems. Consequently, planets in multi-star systems are not well-understood. Planet radius uncertainty is currently limited by the precision on the stellar radius, and in multi-star systems, stellar parameters are often biased by the presence of the stellar companion. To address this, we obtained spectra for both components of the binary star system TOI-2318, which are separated by 0.44’’, with the AO-fed PARVI spectrograph. With a spatial resolution of 0.08’’ in H, PARVI can observe stellar components as close as a few au for the nearest stellar systems. Our spectra of TOI-2318 A and B, combined with accurate Gaia parameters, allow us to establish the stellar parameters for each component to ~10%. These spectra also allow us to determine activity, rotation, component spectral types, and which star in the binary system hosts the orbiting planet. This pilot program is the start of a long-term, multi-instrument study to obtain bulk density measurements at the ~3 sigma level, with the intention to understand how planet formation and evolution may differ between single- and multi-star systems.