S1·E12 Why!? The Night Before the Climactic Battle: Taneshima's Returned Favor

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.