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We present a first statistical sample of faint type-1 AGNs at $z>4$identified by JWST/NIRSpec deep spectroscopy. Among the 185 galaxies at$z_\mathrm{spec}=3.8-8.9$ confirmed with NIRSpec, our systematic search forbroad-line emission reveals 10 type-1 AGNs at $z=4.015-6.936$ whose broadcomponent is only seen in the permitted H$\alpha$ line and not in the forbidden[OIII]$\lambda$5007 line that is detected with greater significance thanH$\alpha$. The broad H$\alpha$ line widths of $\mathrm{FWHM}\simeq1000-6000\\mathrm{km\ s^{-1}}$ suggest that the AGNs have low-mass black holes with$M_\mathrm{BH}\sim10^6-10^8\ M_\odot$, remarkably lower than those oflow-luminosity quasars previously identified at $z>4$ with ground-basedtelescopes. JWST and HST high-resolution images reveal that the majority ofthem show extended morphologies indicating significant contribution to thetotal lights from their host galaxies, except for three compact objects two ofwhich show red SEDs, probably in a transition phase from faint AGNs to lowluminosity quasars. Careful AGN-host decomposition analyses show that theirhost's stellar masses are systematically lower than the local relation betweenthe black hole mass and the stellar mass, implying a fast black hole growthconsistent with predictions from theoretical simulations. A high fraction ofthe broad-line AGNs ($\sim5\%$), higher than $z\sim0$, indicates that a numberdensity of such faint AGNs is higher than an extrapolation of the quasarluminosity function, implying a large population of AGNs including type 1 andtype 2 in the early universe. Such faint AGNs contribute to cosmicreionization, while the total contribution is not large, up to $\sim50\%$ at$z\sim6$, because of their faint nature.

A JWST/NIRSpec First Census of Broad-Line AGNs at z=4-7: Detection of 10 Faint AGNs with M_BH~10^6-10^8 M_sun and Their Host Galaxy Properties