In this presentation, we report our discovery of "blue-excess" dust-obscured galaxies (BluDOGs). DOGs are faint in optical but very bright in mid-infrared (mid-IR), which are powered by active star-formation or AGN, or both. DOGs are believed to be a candidate population that is evolving to a quasar from a gas-rich mergers. On the other hand, a few hot dust-obscured galaxies (Hot DOGs) whose dust temperatures are higher than usual dust-obscured galaxies show a "blue excess" in optical bands. The blue excess is thought to be leaked AGN light. However, the nature of their blue-excess feature and the evolutionary picture among DOGs and HotDOGs with blue-excess are observationally still unclear. By combining three multi wavelength catalogues of optical (Subaru HSC), near-IR (VIKING), and mid-IR (ALLWISE), we have discovered 571 DOGs. By examining the spectral energy distribution in optical, we found that a few DOGs shows an extremely blue color (BluDOGs). The possible origins of this blue-excess are the leaked AGN light and/or stellar UV light from a nuclear starburst. We discuss a possibility that the BluDOGs are in the transition phase from obscured AGNs to unobscured AGNs.