I don't speak any Japanese (beyond domo arigato Mr Roboto, sushi and sashimi) so the meaning and purpose of this game eludes me but there is enough English in there to get the gist.
Essentially, you click and drag your mouse across the screen (in line with the arrow) to give your opponent a good slap - or to dodge their slap. Speed and accuracy seem to be factors.
I managed to get through 3 fights before going down to the slightly demonic looking harridan above.