  We study the modulus mediation of supersymmetry breaking motivated by
superstring theory. We show that the renormalization group running of the soft
supersymmetry breaking parameters due to the interactions of massive fields is
canceled by the threshold corrections at one-loop order, if their mass is given
by nonperturbative dynamics controlled by the same modulus that mediates
supersymmetry breaking and a sum rule of the modular weights holds for the
Yukawa couplings. As an example, we discuss order reduction of lepton flavor
violation in the supersymmetric seesaw mechanism, which revives the parameter
space already excluded.
