Most studies of butterfly flight based on three-dimensional analysis have been performed in artificially confined conditions. We performed this study in completely natural conditions, focusing on freely flying males of territorial lycaenid Favonius taxila. They flew fastest in chasing flight and slowest in fighting (circling) flight. Flight velocity and directional change were negatively correlated. Acceleration at take-off and deceleration at landing were 15.8 m/s² and –6.5 m/s², respectively, at the inflection point of a fitted sigmoid curve. A pursuing tendency in interaction flights was objectively confirmed by constructing a path similarity graph based on individual distance with time shift; in fighting flights with simple patterns, a single peak was observed, indicating that one individual pursued, and in fighting flights with complex patterns, two peaks were observed, indicating that both individuals pursued each other. The form of fighting flights of the present species was far from a so-called “circling flight”, but rather was composed of an irregular combination of distorted small circles. Aggressive acts against the wing of conspecific males were observed in a brief model experiment.