Schematic plot of an EMRI system perturbed by an external SMBH M_e as the tertiary in the system. The tertiary SMBH M_e forms a wider SMBHB with M_•, causing the EMRI center to move around the C.O.M. and thereby inducing an additional LTT modulation in the observed QPE arrival times. The EMRI geometry is described in the coordinate system (x, y, z), while the wider SMBHB is described in the C.O.M. coordinate system (X, Y, Z).