In this episode,Reina and jyunko played together "snipai72",that is a pachinko and well known as a "Oshiri penpen time".
This "oshiri pen pen" means spank(ing),especially for kids by mom,so we can spank girls a lot in bonus stage.
cf.Oshiri means bottom or butt,but we seldom use "pen pen" itself as a "hit or smack/slap".
After enjoying this game,Reina was punished indeed because she lose a game,over her skirt and only a one time.