The existence of competitive equilibria has been extensively studied in many economic models. In the literature of matching theory, attention has been paid to many-to-one matching models. These models consider matching between two types of agents, such as firms and workers, sellers and buyers, hospitals and doctors, or schools and students. In a many-to-one matching model with continuous transfers and quasilinear utilities, the gross substitutes condition (GS), which excludes the complementarity among workers in a firm's valuation, guarantees the existence of competitive equilibria. While GS is known to be a necessary condition in the maximal domain sense, competitive equilibria can exist even if GS is violated. Recent developments in this field have revealed that various conditions other than GS can guarantee the existence of competitive equilibria. For example, under the gross substitutes and complements condition (GSC), competitive equilibria exist even when certain types of complement. The concept of unimodular demand types includes both GS and GSC as special cases.