Previous simulation studies suggest that dust-obscured AGNs appear for a certain period when merger-driven star-forming galaxies evolve to unobscured AGNs. The dust-obscured AGNs would have red colors due to the dust extinction from their host galaxies, and they are expected to have enhanced black hole activities than unobscured AGNs. Red AGNs have very red colors, and they have been suspected as the intermediate-stage, dusty AGNs. However, it is not yet clear if red AGNs really correspond to the dusty young AGNs due to a lack of intrinsic properties of red AGNs. For unveiling the intrinsic properties of red AGNs, we study unobscured and red AGNs. There are three main themes: (i) derivation of new black hole mass estimators that can be used for red AGN study; (ii) investigation of red AGN selection methods to test its usefulness to identify dusty red AGNs; and (iii) investigation of the accretion rates of red AGNs to see if they have the properties as predicted in the simulation studies.