We present the results of our spectroscopic observations of eight detached eclipsing binaries (DEBs), selected from the Kepler Eclipsing Binary Catalog. Radial velocities (RVs) were calculated from high-resolution spectra obtained with the HIgh-Dispersion Echelle Spectrograph (HIDES) spectrograph, attached to the 1.88-m telescope of the Okayama Astrophysical Observatory, and were used to characterize the targets in combination with the Kepler light curves. For each binary, we obtained a full set of orbital and physical parameters, reaching precision below 3 per cent in masses and radii for five pairs. By comparing our results with theoretical models, we assess the distance, age and evolutionary status of the researched objects. We also study eclipse timing variations of selected objects, and identify a new system with a {gamma} Dor pulsator. Two systems are triples, and show lines coming from three components. In one case, the motion of the outer star and the perturbation in the RVs of the inner binary are clearly visible and periodical, which allows us to directly calculate the mass of the third star and inclination of the outer orbit. In the second case, we only see a clear motion of the tertiary and investigate two scenarios: that it is a linear trend coming from the orbital motion around the inner binary and that it is caused by a planetary mass companion. When possible, we also compare our results with the literature, and conclude that only by combining photometry with RVs, it is possible to obtain correct physical parameters of both components of a DEB.