To embody an infinite memory time for the bistable chiral splay nematic liquid crystal (BCSN LC) device, we propose a multidomain structure in which a g/2 twist domain is formed around the BCSN LC device. We investigate how the multidomain structure of the BCSN LC device affects the propagation of a disclination line using a subpixel model. By analyzing the multidomain structure using the subpixel model, the free energy is minimized when the disclination line is located at the boundary between the two different domains. We also demonstrate experimentally that, by forming a g/2 twist domain around the pixel of the BCSN LC device, the propagation of the disclination line can be prevented and an infinite memory time can be achieved.