We utilized bi-crystals with an artificially designed grain boundary configuration as a seed for floating-zone growth of multicrystalline Si (mc-Si) in order to clarify the impact of the initial grain boundary configuration on the crystal growth. Intentionally introduced large tilt deviation from Σ3 was found to lead to appearance of new crystal grains accompanied by spontaneous modification of the grain boundary to electrically inactive Σ3 under appropriate amount of the supercooling. Based on this mechanism, a model crystal growth experiment was performed to realize mc-Si with electrically inactive grain boundaries using purposely designed 〈110〉-oriented seed crystal with an array of random grain boundaries. After 40 mm growth, all the grain boundaries were revealed to be modified to electrically inactive. These results suggest that bulk mc-Si with electrically inactive grain boundaries could be grown even by the practical casting method if oriented crystal grains with random grain boundaries could be somehow realized at the bottom of the crucible.