Put simply, Momo is a superstar who is recognised everywhere that she goes - not surprising considering the fact that she's plastered over televisions, billboards and goodness knows what else all around her home city in spite of only being a first-year high school student. By all accounts, it looks as if she might stay that way too, as a discussion with her teacher after turning up late to school confirms that she's far from the sharpest tool in the box - if it isn't knowledge about manga, Kisaragi probably doesn't know it.
Although she outwardly seems to be your typical, cheerful idol type, there is a sadder side to Momo's story - having lost her father at a young age, she proved herself capable of winning the plaudits of others in a multitude of disciplines. However, the flip side of this is that she's been left friendless as a result, as others with more obvious talent have always been frustrated by her easy way of winning people over and grabbing their attention without really doing anything noteworthy at all - a fact which has followed her all of the way through her life to her career as an idol. It also emerges that Momo is being watched by somebody, which in turn ties into some of the events surrounding episode one beyond the fact that she's Shintaro's sister.
If nothing else, this second episode of Mekakucity Actors was at least an improvement over the first - Momo's character is both easier to like and to engage with than Shinataro, and alongside this the episode itself was more compelling in terms of both SHAFT's visual flourishes and the story that it told. How this services the wider narrative of the story remains to be seen, but I am a little buoyed by the this more accomplished effort when it comes to hoping for something more interesting from the series as a whole, even if parts of it still felt a little like a low-rent Bakemonogatari.