1. An information processing assistance device, comprising: an improved main function generation unit generating an improved main function by: determining whether a vector part image of a vector image is changed by determining whether a group of sub-functions is updated without drawing a raster image from the part of the vector image, the raster image being drawn from the vector part image when the group of sub-functions is executed; and adding, when the vector part image of the vector image is determined to be changed, the group of sub-functions and a cache function to a main function, the raster image drawn from the changed vector part image being cached when the cache function is executed, wherein the raster image is displayed on a user device when the main function is executed, and wherein the group of sub-functions are called in succession and in a predetermined order from a common call source when the main function includes the group of sub-functions and the main function is executed.