  We investigate the impact of extra leptons on observed tensions in the muon
$g-2$ and the first-row CKM unitarity. By introducing a new SU(2)$_L$ doublet
lepton and a SU(2)$_L$ triplet lepton, we find that both of the tensions can be
explained simultaneously under constraints from electroweak precision
observables and Higgs-boson decays. Our model could be tested by measurements
of $h\to\mu\mu$ at future collider experiments.
