  We present demography of the dynamics and gas-mass fraction of 33 extremely
metal-poor galaxies (EMPGs) with metallicities of $0.015-0.195~Z_\odot$ and low
stellar masses of $10^4-10^8~M_\odot$ in the local universe. We conduct deep
optical integral-field spectroscopy (IFS) for the low-mass EMPGs with the
medium high resolution ($R=7500$) grism of the 8m-Subaru FOCAS IFU instrument
by the EMPRESS 3D survey, and investigate H$\alpha$ emission of the EMPGs.
Exploiting the resolution high enough for the low-mass galaxies, we derive gas
dynamics with the H$\alpha$ lines by the fitting of 3-dimensional disk models.
We obtain an average maximum rotation velocity ($v_\mathrm{rot}$) of
$15\pm3~\mathrm{km~s^{-1}}$ and an average intrinsic velocity dispersion
($\sigma_0$) of $27\pm10~\mathrm{km~s^{-1}}$ for 15 spatially resolved EMPGs
out of the 33 EMPGs, and find that all of the 15 EMPGs have
$v_\mathrm{rot}/\sigma_0<1$ suggesting dispersion dominated systems. There is a
clear decreasing trend of $v_\mathrm{rot}/\sigma_0$ with the decreasing stellar
mass and metallicity. We derive the gas mass fraction ($f_\mathrm{gas}$) for
all of the 33 EMPGs, and find no clear dependence on stellar mass and
metallicity. These $v_\mathrm{rot}/\sigma_0$ and $f_\mathrm{gas}$ trends should
be compared with young high-$z$ galaxies observed by the forthcoming JWST IFS
programs to understand the physical origins of the EMPGs in the local universe.
