  We report first precision mass measurements of the $1/2^-$ isomeric and
$9/2^+$ ground states of $^{101}$In. The determined isomeric excitation energy
continues a smooth trend of odd-$A$ indium isotopes up to the immediate
vicinity of $N=50$ magic number. This trend can be confirmed by dedicated shell
model calculations only if the neutron configuration mixing is considered. We
find that the single particle energies are different for different states of
the same isotope. The presented configuration-dependent shell evolution, type
II shell evolution, in odd-$A$ nuclei is discussed for the first time. Our
results will facilitate future studies of single-particle neutron states.
