The IKKT matrix model in the large-$N$ limit is conjectured to be a non-perturbative definition of the ten-dimensional type IIB superstring theory. Due to the Pfaffian's inherently complex nature upon Euclideanization, the model has a severe sign problem. The phase of the Pfaffian plays a critical role in determining the correct vacuum of the model. In recent years, the complex Langevin method has been proved to tackle the sign problem successfully. In this talk, we discuss our results from the complex Langevin simulations of the Euclidean version of the IKKT model. We investigate the possibility of spontaneous breaking of $SO(10)$ rotational symmetry. The model must be deformed to evade the singular drift problem during complex Langevin simulations. We recover the original model in the vanishing deformation parameters limit. In addition to mass deformations that explicitly break supersymmetry, we introduce supersymmetry-preserving deformations with a Myers term. We conclude that the phase of the Pfaffian indeed induces the spontaneous breaking of the $SO(10)$ rotational symmetry in the Euclidean IKKT matrix model.