Theory and simulation allow to identify a process of SPONTANEOUS reconnection based on the features of a nonlinear kinetic structure, the Forced Kinetic Current Sheet (FKCS). The process is independent of the triggering disturbance, and appears to be spontaneously self-sustained, as a finite magnitude MHD disturbance of a rarefaction wave type propagates back over the background plasma outside the CS. Transformation of electromagnetic energy into the energy of plasma flows occurs at the FKCS. Generation of "free" energy takes place in the course of that transformation: strongly anisotropic ion distributions are produced. Further dissipation of that "free" energy leads to an effect of magnetic field "annihilation", which is a necessary constituent of fast magnetic reconnection.