In this paper, we recall some previous research of a bijection between transitive digraphs and topologies on a finite set. In data science area, k Nearest Neighbor(kNN) graph is widely used graph. It can be interpreted by a digraph in the sense of in and out degrees. kNN graph is not transitive in general. Adding or eliminating edges, there are many methods to get a transitive digraph from a given kNN graph. In this paper, we show there is unique way which make a transitive digraph preserving topology. Moreover, we suggest a simple method to make the transitive digraph without computing topology.