Recently, dualities among W-superalgebras and their affine cosets conjectured by Gaiotto-Rapcak have been established in many cases by Creutzig-Linshaw and Creutzig-Linshaw-Kanade by using universal objects of such algebras. Independently, Creutzig-Genra and I proved the duality in the case of subregular W-algebras and principal W-superalgebras of type A by using free field realizations of those algebras. This point of view upgrades the duality to a "reconstruction theorem" of one of the algebra from the other one. The simplest example is the Kazama-Suzuki coset construction of N=2 superconformal algebra from the affine sl2 vertex algebra and its inverse by Feigin-Semikhatov-Tipunin. In this talk, I will explain this reconstruction theorem and then its application to the representation theory of principal W-superalgebra side in the rational cases. This talk is based on on-going project with Thomas Creutzig, Naoki Genra and Ryo Sato