  Fifth forces are ubiquitous in modified gravity theories, and must be
screened to evade stringent local tests. This can introduce unusual behaviour
in galaxy phenomenology by affecting galaxies' components differently. Here we
use the SDSS-IV-MaNGA dataset to search for a systematic excess of gas circular
velocity over stellar circular velocity, expected in thin-shell-screened
theories in the partially screened regime. Accounting for asymmetric drift and
calibrating our model on screened subsamples, we find no significant evidence
for a screened fifth force. We bound the fifth-force strength to $\Delta
G/G_\text{N} < 0.1$ for all astrophysical ranges, strengthening to $\sim$0.01
at Compton wavelength of 3 Mpc for the Hu-Sawicki model, for instance. This
implies a stringent constraint on scalar-tensor theories, for example
$f_{\mathcal{R}0} \lesssim 10^{-8}$ in Hu-Sawicki $f(\mathcal{R})$ gravity.
