  We developed a four-dimensional Langevin model which can treat the
deformation of each fragment independently and applied it to low energy fission
of 236U, the compound system of the reaction n+$^{235}$U. The potential energy
is calculated with the deformed two-centerWoods-Saxon (TCWS) and the Nilsson
type potential with the microscopic energy corrections following the Strutinsky
method and BCS pairing. The transport coefficients are calculated by
macroscopic prescriptions. It turned out that the deformation for the light and
heavy fragments behaves differently, showing a sawtooth structure similar to
that of the neutron multiplicities of the individual fragments $\nu$(A).
Furthermore, the measured total kinetic energy TKE(A) and its standard
deviation are reproduced fairly well by the 4D Langevin model based on the TCWS
potential in addition to the fission fragment mass distributions. The developed
model allows a multi-parametric correlation analysis among, e.g., the three key
fission observables, mass, TKE, and neutron multiplicity, which should be
essential to elucidate several long-standing open problems in fission such as
the sharing of the excitation energy between the fragments.
