In the framework of the Faddeev equations in configuration space we perform an analysis of quasi-bound state of the NN{\bar K}NNK‾ system within a particle model. In our approach, the system NN{\bar K}(s_{NN}=0)NNK‾(sNN=0) (NN{\bar K}(s_{NN}=1))NNK‾(sNN=1)) is described as a superposition of ppK^{-}ppK− and pn{\bar K}^0pnK‾0 (nn{\bar K}^{0}nnK‾0 and pn{ K}^-pnK−) states, which is possible due to a particle transition. The relation of the particle model to the theory of a two-state quantum system is addressed and discussed taking into account the possibilities of deep and shallow NN{\bar K}(s_{NN}=0)NNK‾(sNN=0) quasi-bound states.