  We present kinematics of 6 local extremely metal-poor galaxies (EMPGs) with
low metallicities ($0.016-0.098\ Z_{\odot}$) and low stellar masses
($10^{4.7}-10^{7.6} M_{\odot}$). Taking deep medium-high resolution
($R\sim7500$) integral-field spectra with 8.2-m Subaru, we resolve the small
inner velocity gradients and dispersions of the EMPGs with H$\alpha$ emission.
Carefully masking out sub-structures originated by inflow and/or outflow, we
fit 3-dimensional disk models to the observed H$\alpha$ flux, velocity, and
velocity-dispersion maps. All the EMPGs show rotational velocities ($v_{\rm
rot}$) of 5--23 km s$^{-1}$ smaller than the velocity dispersions
($\sigma_{0}$) of 17--31 km s$^{-1}$, indicating dispersion-dominated ($v_{\rm
rot}/\sigma_{0}=0.29-0.80<1$) systems affected by inflow and/or outflow. Except
for two EMPGs with large uncertainties, we find that the EMPGs have very large
gas-mass fractions of $f_{\rm gas}\simeq 0.9-1.0$. Comparing our results with
other H$\alpha$ kinematics studies, we find that $v_{\rm rot}/\sigma_{0}$
decreases and $f_{\rm gas}$ increases with decreasing metallicity, decreasing
stellar mass, and increasing specific star-formation rate. We also find that
simulated high-$z$ ($z\sim 7$) forming galaxies have gas fractions and dynamics
similar to the observed EMPGs. Our EMPG observations and the simulations
suggest that primordial galaxies are gas-rich dispersion-dominated systems,
which would be identified by the forthcoming James Webb Space Telescope (JWST)
observations at $z\sim 7$.
