  The void ellipticity distribution today can be well explained by the tidal
field. Going a step further from the overall distribution, we investigate
individuality on the tidal response of void shape in non-linear dynamical
evolution. We perform an N-body simulation and trace individual voids using
particle ID. The voids are defined based on Voronoi tessellation and watershed
algorithm, using public code VIDE. A positive correlation is found between the
time variation of void ellipticity and tidal field around a void if the void
maintains its constituent particles. Such voids tend to have smaller mass
densities. Conversely, not a few voids significantly deform by particle
exchange, rather than the tidal field. Those voids may prevent us from
correctly proving a quadrupole field of gravity out of a void shape.
