Normal Sally modules of rank one

In this paper, we explore the structure of the normal Sally modules of rank one with respect to an $m$-primary ideal in a Nagata reduced local ring which is not necessary Cohen-Macaulay. As an application of this result, when the base ring is Cohen-Macaulay analytically unramified, the extremal bound on the first normal Hilbert coefficient leads to the Cohen-Macaulayness of the associated graded rings with respect to a normal filtration.