Can Xu, John D. Silverman, Qiusheng Gu, Daniela Galárraga-Espinosa, Andreas L. Faisst, Emanuele Daddi, Hassen M. Yesuf, Angelo George, Esra Bulbul, Zeyu Gao, Lalitwadee Kawinwanichakij, Takumi S. Tanaka, Yunjing Wu, Jialai Wang, Michiru Maruyama

We investigate how cluster environments affect galaxy star formation, structure, and stellar populations using spectroscopically-confirmed galaxies in X-ray-selected eROSITA clusters, that have deep HSC-SSP imaging and DESI DR1 spectroscopy. At 0.1<z<0.5, we compare dust-corrected Ha star formation rates (SFRs), effective radii (Re), bulge-to-total light ratios (B/T), and Dn4000 between cluster satellites and a stellar-mass- and redshift-matched field control sample. We identify UVJ-quiescent galaxies and divide the UVJ star-forming population at log(sSFR_Ha)= -10.5 yr-1 into actively star-forming and Ha-low systems, the latter referred to as green-valley (GV) galaxies. Cluster--field differences depend strongly on stellar mass, projected cluster-centric radius, and galaxy population. Cluster star-forming galaxies show modest SFR suppression but weak structural offsets. The strongest coupled signatures occur among Ha-low UVJ-star-forming galaxies, particularly low-mass satellites at R<0.5R500, which have lower SFRs, smaller light-weighted sizes, larger B/T, and larger Dn4000 than matched field counterparts. Quiescent galaxies show weaker structural offsets but retain a positive Dn4000 residual. We quantify the joint signal using a Mahalanobis distance based on matched residuals in SFR, Re, B/T, and Dn4000 with a field--field reference covariance. The multivariate offset is largest for low-mass GV galaxies and decreases toward larger projected radius. The broader radial extent of SFR suppression relative to structural offsets suggests that star-formation suppression has a broader environmental reach than structural transformation. These results show that environmental quenching and structural transformation are most strongly coupled in the Ha-low transition population.