Though there were many themes presented throughout Mawaru Penguindrum, a theme that many young adults these days are actually living was heavily touched upon in the first third of the series. But first: if you can recall, the first third of the series didn’t have crazy plot twist after crazy plot twist dealing with Himari and her brothers, but it instead focused almost exclusively on the life and times of Oginome Ringo, and her relentless devotion to reliving Momoka’s diary.
While on the surface it looked as though Ringo was doing anything necessary to be able to be with Keiju, the ultimate conclusion to this arc, in which Ringo can’t seal the proverbial deal with Keiju, and in which she loses half of Momoka’s diary (and, later, the second half) suggest that Ringo’s actions had a deeper meaning. From the beginning, Ringo was following a list of directives that she believed would lead her to a happier life. If we put aside some parts of the plot involving Ringo wanting to take the place of her sister to make her parents happy, the directives that Ringo blindly follows are similar in nature to the steps children and adolescents think they need to as they grow up, like a ritual or rite of passage. And, as the arc progressed, Ringo began interpreting the diary more and more liberally as a way to keep the possibility of fulfilling her “destiny” alive. Or was she?
The way the story was laid out, the case could easily be made that Ringo’s increasingly bizarre actions from interpreting her sister’s diary was a response to the adverse reactions she experienced to symbolic events of adolescence. Two examples that illustrate this point are the whole frog fiasco in episode 7 (Why else have a slimy frog lay an egg) and monthly curry dinner with her mother that had gone astray. Taking it to the next level, combining these two examples with her ultimate freak out with Keiju, illustrates that Ringo didn’t know how to handle what was going on with her body.
During this period of the show, there was also a small, but still important and recurring segment featuring Masako erasing young girls’ memories with her slingshot. Viewing these memory impaired girls separately from Ringo would be a big mistake. Let’s consider that the girls in episode 6 seemed like they had been jilted by Kanba in the past, but Ringo did not cross that line with Keiju. Now while it seems like a stretch to view Masako and Ringo’s routes as interrelated, especially considering they hardly interact, Ringo eventual gave the remaining half of her diary to Masako, suggests that she gave up/delayed taking the next step in her life before she had something worth forgetting (via a red ball to the forehead).
Following this first main arc of the series, Ringo’s presence within the anime diminishes for some time, only to reemerge near the end of the story. During this time, Ringo and Shoma definitely have some level of a relationship, but it was obviously complicated (and honestly, not that well portrayed). Eventually, Ringo was at least able to break free of the diary’s directives, and able to explore life with a less than ideal relationship with Shoma. I think in the end, Ringo’s use of Momoka’s phrase, after the diary had already burned shows that she matured over the course of last 2/3rd of the series, and that she was able to do so at her own pace.