We consider the modified scattering problem for the nonlinear Klein–Gordon equation with cubic nonlinear interactions in one spatial dimension 1 \(\begin{aligned} {\left\{ \begin{array}{ll} w_{tt}-\Delta w+w=\mu |w|^{2}w,\\ w\left( 0,x\right) =w_{0}\left( x\right) , w_{t}\left( 0,x\right) =w_{1}(x), \end{array}\right. } \end{aligned}\) for \(\mu \in \mathbb {R}\) . We show that for any small real valued initial data \(w_{0},\) \(w_{1}\) low-regularity weighted Sobolev spaces there exists a unique modified final state \(W_{+}\in \textbf{L}^{\infty }\) such that the corresponding solution exhibits a logarithmic phase correction as \(t\rightarrow \infty .\) Our proof is based on the Factorization Technique. We present more simple and robust method for the proof of this result based on the Factorization Technique and on the \(\textbf{L}^{2}\) - estimates for the transformed evolution operators, which considerably simplifies the proof of the asymptotics of solutions.