  We report ALMA Band 3 observations of CO(6-5), CO(7-6), and [CI](2-1) in
B14-65666 (``Big Three Dragons''), one of the brightest Lyman-Break Galaxies at
$z>7$ in the rest-frame ultraviolet continuum, far-infrared continuum, and
emission lines of [OIII] 88 $\mu$m and [CII] 158 $\mu$m. CO(6-5), CO(7-6), and
[CI](2-1), whose $3\sigma$ upper limits on the luminosities are approximately
40 times fainter than the [CII] luminosity, are all not detected. The $L_{\rm
[CII]}$/$L_{\rm CO(6-5)}$ and $L_{\rm [CII]}$/$L_{\rm CO(7-6)}$ ratios are
higher than the typical ratios obtained in dusty star-forming galaxies or
quasar host galaxies at similar redshifts, and they may suggest a lower gas
density in the photodissociated region in B14-65666. By using the (1) [CII]
luminosity, (2) dust mass-to-gas mass ratio, and (3) a dynamical mass estimate,
we find that the molecular gas mass ($M_{\rm{mol}}$) is
$(0.05-11)\times10^{10}$ $M_{\rm \odot}$. This value is consistent with the
upper limit inferred from the nondetection of mid-$J$ CO and [CI](2-1). Despite
the large uncertauinty in $M_{\rm mol}$, we estimate a molecular gas-to-stellar
mass ratio ($\mu_{\rm{gas}}$) of $0.65-140$ and a gas depletion time
($\tau_{\rm dep}$) of $2.5-550$ Myr; these values are broadly consistent with
those of other high-redshift galaxies. B14-65666 could be an ancestor of a
passive galaxy at $z\gtrsim4$ if no gas is fueled from outside the galaxy.
