  We perform the stability analysis of the Kerr black hole in the
Einstein-Chern-Simons-Scalar theory with quadratic scalar coupling. For
positive coupling parameter ($\alpha>0$), we introduce the (2+1)-dimensional
hyperboloidal foliation method to show that the Kerr black hole is unstable
against scalar-mode perturbation. In case of $\alpha<0$, it is shown that the
Kerr black hole is unstable without any $\alpha$-independent bound on the
rotation parameter $a$ when using the the hyperboloidal foliation method. The
disappearance of the $a$-bound is confirmed analytically by implementing the
(1+1)-dimensional linearized scalar equation.
