One of the purposes of fusion simulations is to develop a code that could predict the entire temporal behavior of experimentally observed macroscopic physics quantities under continuous external control, which will be used to create the path to helical-type reactor by combining knowledge of reactor design. In this paper an integrated simulation code system for three-dimensional toroidal helical plasmas in the Large Helical Device (LHD) is reported. This code has been developed under the domestic and international research collaborations among universities and institutes. After explaining the structure of the code system, including the transport simulation code TASK3D and the magnetohydrodynamic (MHD) equilibrium and stability code MHD3D, we present typical simulation results: evolution of the rotational transform, MHD stability beta limit, and recent progress in the TASK3D code.