K-ON!! Season 2 episode #14
It's the day before classes start again, and Ritsu wants to hang out.
It's the day before the start of the summer classes. Ritsu calls Mio hoping she would hang out with her, but she was studying and hangs up. Ritsu spots Mugi and secretly follows her, only knowing that she was the one secretly spotted by Mugi. Mugi realizes this is the first time she can hang out with just Ritsu, and requests her to take her to "normal" places. They go to an arcade, where Ritsu wins a stuffed doll for Mugi. Then, they go to a candy store and Ritsu teaches Mugi how to eat "normal" things priced at only 20 to 30 yen. They eat out, and Mugi begs Ritsu of one thing: to hit her, since she realizes the intimacy of Mio and Ritsu hitting each other, or even Yui pouncing on Azusa, and she was missing on it.
The next day, the start of summer classes, Mio wears her school uniform while they aren't still supposed to. Ritsu and Mugi plan on how to get Mio to hit Mugi, but fail. The next day in the music room, there was an extra slice of strawberry cake. Ritsu takes the chance and suggest they play a game: whoever wins will get the extra slice of cake, and whoever loses will get hit on the forehead. Ritsu whispers to Mugi to lose, but Mugi inadvertently wins and Ritsu loses.
As they eat, Mugi recalls a small conversation between Yui and Mio concerning the strawberry on the cake. When Mio was about to fork her topped strawberry, Mugi forks and eats it. Upon seeing her strawberry stolen from her, Mio's eyes fill with tears. Yui dragged Nodoka (who a few days earlier she had a slight argument with over the strawberry on a slice of cake) over to show that the topping of the cake is most important. Finally, Ritsu and Mugi revealed what Mugi is after. Despite their admittance and insistence on Mio hitting Mugi for what she just did, Mio can't bring herself to do it and hits Ritsu instead.
While walking, Mugi finally gets hit hard by Ritsu when she says that Ritsu would have been more popular if she was a boy.