  On the route towards merging neutron stars and stripped-envelope supernovae,
binary population synthesis predicts a large number of post-interaction systems
with massive stars that have stripped off their outer layers. Yet, observations
of such stars in the intermediate-mass regime below the Wolf-Rayet masses are
rare. Using X-Shooting ULLYSES (XShootU) data, we discovered three partially
stripped star + Be/Oe binaries in the Magellanic Clouds. We analyzed the UV and
optical spectra using the PoWR model atmosphere code by superimposing model
spectra corresponding to each component. The estimated current masses of the
partially stripped stars fall within the intermediate mass range of 4-8
$M_{\odot}$. These objects are overluminous for their stellar masses, matching
core He-burning luminosities. Their Be/Oe secondaries have much higher masses
than their stripped primaries (mass ratio > 2). All three partially stripped
stars show significant nitrogen enrichment and carbon and oxygen depletion on
their surfaces. Additionally, one of our sample stars exhibits significant
helium enrichment. Our study provides the first comprehensive determination of
the wind parameters of partially stripped stars in the intermediate mass range.
The wind mass-loss rates of these stars are found to be on the order of
$10^{-7} M_\odot$ yr$^{-1}$, which is over ten times higher than that of OB
stars of the same luminosity. Current evolutionary models characterizing this
phase typically employ OB or WR mass-loss rates, which underestimate or
overestimate stripped stars' mass-loss rates by an order of magnitude. Binary
evolution models indicate that the observed primaries had initial masses of
12-17 $M_{\odot}$, making them potential candidates for stripped-envelope
supernovae that form neutron stars. If they survive the explosion, these
systems may become Be X-ray binaries and later double neutron stars.
