A virtual reality (VR) system for Monte Carlo (MC) transport simulation codes, MCNP and Particle and Heavy Ion Transport Code System (PHITS), was developed. This system is aimed to provide a more reliable confirmation of the simulation geometry through an intuitive user interface. The VR system is implemented by extending the Geometry and CROSS Section VIEWer (Gxsview) code to run in a JavaScript environment, and it takes advantage of web technology and does not require dedicated hardware or geometry information supplied by computer-aided design software. Therefore, only WebXR-compatible head-mounted displays and browsers are required on the user side. In the VR space, visualization of the calculation geometry, cell selection, and cell grabbing operations is possible with a handheld controller. Further enhancements will be made in the future, such as performing shielding calculations with the cell changed by grabbing operations.