It has been a long-standing problem to analytically prove confinement of pure Yang-Mills theory. One possible scenario is to start with the weakly-coupled region, obtain the trans-series expansion with respect to gauge coupling constant, and then continue back to the strongly-coupled region, with the help of mathematics of “resurgence”. The program has been pursued mostly on the geometry R^3 x S^1, however there the trans-series expansion could be spoiled by IR divergences. In this talk we discuss 4d SU(N) Yang-Mills theory on R×T^3, with twisted boundary condition eliminating IR zero modes. By connecting the 4d Yang-Mills theory to 2d CP^{N-1}-model, we find that the fractional instantons connecting N vacua of the CP^{N-1}-model dynamically restores center symmetry. This talk is based on arXiv:1704.05852, in collaboration with Kazuya Yonekura.