Megumi Sokabe

Megumi Sokabe was formerly both the president of Sakuragaoka High School's student council and (secretly) the president of the Mio Akiyama Fan Club. Nodoka Manabe succeeds her in both roles after Megumi graduates (reluctantly in the latter case). Megumi is revealed to have been stalking Mio towards the end of her third year, but only because she would miss Mio once she graduated, since she adores her. The Light Music Club gave her a private concert as a graduation gift, which she said she enjoyed after pretending to berate the club for using the auditorium without permission.

After she had graduated, Nodoka lamented that her actions as the fan club's president weren't worth much compared to Megumi's, so the club held a tea party for the fan club and invite Megumi over. Unfortunately, she couldn't come because she had to attend University, so Azusa Nakano sent her a picture of the party with her mobile phone, much to Megumi's pleasure.

In the manga, when Ritsu Tainaka and the rest are about to graduate, it was revealed that Ritsu and Megumi are actually close friends (although it was never revealed how that came to be). In that chapter, Megumi lent Ritsu her notes for entrance exam preparation for her current university, which is the all-girl university that the other girls want to enter together. Ritsu then took a suggestion from Nodoka and gave Megumi a photo of Mio as a thank-you-gift.

In the restart of the K-ON! Manga, Megumi reappears, sharing her dormitory with Yui Hirasawa, Mio, Ritsu and Tsumugi Kotobuki during their tenure in J. Women's University. She had laughed at Ritsu's bangs-down hairstyle before fixing it.

Trivia

 * There is a discrepancy between Megumi's appearances in the first and second seasons of the anime. In the first broadcast of the second season, Megumi's bow was red, so she was depicted as a third year student while the senior Light Music Club members were freshmen. This was supported by the fact that Azusa did not know who Megumi was and also did not perform with the rest of the Light Music Club for her, as explained in Tea Party!. In Crisis! however, she was present when Ritsu and Nodoka begged Megumi to let the Light Music Club perform at the school festival, meaning that Megumi graduated after the original club members' second year of attendance. The error was corrected in the Blu-ray version by changing the colour of Megumi's bow to green (which was the colour of the senior students' bows during the original club members' second year).
 * There is another discrepancy in that Azusa had no idea who Megumi was during Tea Party!, despite the fact that she had been in the room while Ritsu and Nodoka were negotiating with Megumi in Crisis!. The only logical explanation is that Yui, Mio, Ritsu, Tsumugi and Nodoka handled the whole situation behind Azusa's back without informing her at all. This, however, still leaves the problem of Azusa and Megumi meeting, since they were in the same room, although it is possible that since Azusa was not introduced to Megumi, she simply did not remember.