Development of an integrated simulation system for helical plasma is described that draws new experimental plans, including those in new devices, and does experimental data analysis from the viewpoint of integrated physics. The integrated simulation system to be developed has a modular structure that consists of modules for calculating magnetohydrodynamic (MHD) equilibrium/stability, transport, and heating. Each module can be selected in accordance with a user's request and can be combined with other modules. When we want to perform the integrated simulation during the entire plasma duration, a transport module is to be a core module. An integrated tokamak transport code will be extended for the helical configuration and used as a transport module. As the first step of the extension, time evolution of the plasma net current, which is consistent with the three-dimensional MHD equilibrium, is planned to be solved for Large Helical Device plasmas by taking into account the bootstrap current and the beam-driven current.