The Rustic (Cupha erymanthis) is an orange-brown butterfly with a characteristic broad yellow discal patch on the forewings followed by a broad black apical area.
The male and female are identical. 
The Rustic is a relatively common species in Vietnam.
In flight, it can sometimes be mistaken for the Banded Yeoman (Cirrochroa orissa). 
However, in Vietnam the Banded Yeoman is much rarer.
The Rustic is an alert butterfly and is difficult to photograph as it flits from leaf to leaf and rarely stops for long. 
Even when it is perched, its wings are often moving continuously, ready to take off at the slightest distraction.

Cat Ba National Park, Cat Ba Island, Vietnam, 6 January 2024