Eve of the Duel!? Taneshima's Reciprocation.
Pupura finds out about Takanashis tall sisters and is upset with him for keeping these ideal women from her. As punishment she sets him up to go on a date with Mahiru. An experiment to see how much more man acclimated Mahiru has become concludes that if she can't punch Takanashi she'll kick him in the nuts.
Aired 20/06/2010EP 12 - Eve of the Duel!? Taneshima's Reciprocation.

2010
Wagnaria!!
Set in a family restaurant in Hokkaido, the northern prefecture of Japan, 16-year-old high school student Souta Takanashi works part-time along with his strange co-workers: Popura Taneshima, a high school girl who's a year older than Souta, yet easily mistaken for an elementary/middle schooler, and Kyoko Shirafuji, the 28-year-old store manager who doesn't bother to do any work at all.
(Source: NIS America)