We developed a full variational molecular orbital method by which centers and exponents in a Gaussian-type function basis set are optimized automatically, as well as the molecular orbital coefficients. In the present study, we observed the behavior of wave functions with flexible basis functions for fictitiously changing the electron mass to examine the flexibility of the method. We performed two types of computational scientific simulations by decreasing and increasing the electron mass. First, we demonstrated electron transfer together with the basis function on a computer. Second, we studied the change of the wave function of the electron from delocalized to localized by increasing its mass. As test models, we used a Li^-...H⁺ system for the first simulation, and an H₂⁺ ion having a symmetrical potential for the second simulation.