Chu-Bra!! is an interesting fanservice show, because it challenges what the common perception of modesty is. Where other anime or manga series with this sort of context are strictly about fanservice for the viewer, a major plot of this series is the concept of what is too taboo to talk about with teenagers, and even some adults.
Our focus of this series is Nayu Hayama and her love for women's underwear. It's not a perverse lust for underwear for panties like Happosai (from Ranma 1/2) has, but a sincere interest in underwear. Nayu's brother, like her late grandmother, are professional under designers, and their passion for the work and indeed the art of it has been passed on to her as well. Nayu takes a great deal of interest in what people are wearing, the design of their underwear, and weather it is comfortable or not for them. Nayu likes to give advice, and help her friends whenever possible, and is so knowledgeable about underwear she can give proper advice to any girl, no matter what their size is. Nayu is a wonderfully written character because she does mean well, and doesn't look down on anyone when it comes to their size, but she comes across as overbearing at times, and can cross the line when it comes to personal space, even with her close friends.
As I stated before, a main part of this show is the opposing philosophies when it comes to modesty. On one hand, Nayu and her friends want to start an "underwear club" in their high school, not for perverted reasons, but because Nayu understands that high school girls are going through changes and need a support group of some kind to help them understand what is going on with their bodies. The main opposition to the club is a very strict and old fashioned female professor who sees the very notion of an underwear club as nothing but perverse, and something that could bring shame to the school itself if word got around. It's a wonderful dynamic, and it's easy to understand both sides of the argument, and it eventually plays out very well. You really get a real feeling for Nayu and her way of thinking, that underwear is both personal, common, and important.Chu-Bra!! is a very light-hearted series that's easy to watch. There are a few subplots involving other classmates who have it in for Nayu, and a romantic subplot that involves her homeroom professor and her older brother, but even those come across as rather light. It's a very well balanced show given its context. It's a fanservice show with a reasonable plot, and that's not easy to find these days. Give this show a shot if you like light-hearted series like Ichigo Mashimaro, or Popotan.