  Recently, several new experimental results of the test of lepton flavor
universality (LFU) in $B\to D^{(\ast)}$ semi-leptonic decays were announced:
the first result of $R_{D}$ from the LHCb Run 1 data, the first results of
$R_{D}$ and $R_{D^\ast}$ from the LHCb Run 2 data, and the first result of
$R_{D^\ast}$ from the Belle II collaboration. Including these new data, a
global analysis still prefers the violation of the LFU between the tau and
light leptons. A new world average of the data from the BaBar, LHCb, Belle, and
Belle II collaborations is $R_{D} = 0.344 \pm 0.026$ and $R_{D^{\ast}} = 0.285
\pm 0.012$. Including this new data, we update a circumstance of the $b \to c
\tau \overline\nu$ measurements and their implications for new physics (NP).
Incorporating recent developments for the $B \to D^{(\ast)}$ form factors in
the Standard Model (SM), we observe a $4.3 \sigma$ deviation from the SM
prediction. Our updates also include; model-independent NP formulae for the
related observables; and the global fittings of parameters for leptoquark
scenarios as well as single NP operator scenarios. Furthermore, we show future
potential to indirectly distinguish different NP scenarios with the use of the
precise measurements of the polarization observables in $B\to D^{(\ast)}\tau
\overline\nu$ at the Belle II and the high-$p_{\rm T}$ flavored-tail searches
at the LHC. We also discuss an impact on the LFU violation in $\Upsilon \to l^+
l^-$.
