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The nature of the so-called ``changing-look'' (CL) active galactic nucleus(AGN), which is characterized by spectral-type transitions within $\sim10$~yr,remains an open question. As the first in our series of studies, we hereattempt to understand the CL phenomenon from a view of the coevolution of AGNsand their host galaxies (i.e., if CL-AGNs are at a specific evolutionary stage)by focusing on the SDSS local ``partially obscured'' AGNs in which the stellarpopulation of the host galaxy can be easily measured in the integrated spectra.A spectroscopic follow-up program using the Xinglong 2.16~m, Lick/Shane 3~m,and Keck 10~m telescopes enables us to identify in total 9 CL-AGNs from asample of 59 candidates selected by their mid-infrared variability. Detailedanalysis of these spectra shows that the host galaxies of the CL-AGNs arebiased against young stellar populations and tend to be dominated byintermediate-age stellar populations. This motivates us to propose that CL-AGNsare probably particular AGNs at a specific evolutionary stage, such as atransition stage from ``feast'' to ``famine'' fueling of the supermassive blackhole. In addition, we reinforce the previous claim that CL-AGNs tend to bebiased against both a high Eddington ratio and a high bolometric luminosity,suggesting that the disk-wind broad-line-region model is a plausibleexplanation of the CL phenomenon.

Are "Changing-Look'' Active Galactic Nuclei Special in the Coevolution of Supermassive Black Holes and their Hosts? I