Shoujo anime will typically feature romance as part of the main storyline. There are an endless number of shoujo anime and manga on the market revolving around high school romances. The romances in shoujo anime tend to be more idealistic in nature with themes like "love at first sight" or "love has always been at your side." While I hate to make it sound negative, I would rather describe it as the fantasy romance that many girls dream of.

Many characters in shoujo tend to battle some sort of conflict within themselves whether it's something as simple as being painfully shy, having an inferiority complex, or even trying to achieve a dream, but many of the issues are ones that girls do face as adolescents. One really funny series is a manga called Heroine Shikkaku, by Koda Momoko, where the main character Hitori thought of herself as the heroine in her own story who was destined to end up with her childhood friend Rita, and labeled everyone else as a side character from reading too many romance novels.
This actually may affect some teens who are passive and believe that things will just work out in their favor. There's also Fruits Basket, in which Tohru must cope with the loss of both of her parents and attempt to live independently while trying to fulfill the dream of her mother. Many teenagers have to cope with the loss of a loved one so many may be able to sympathize with Tohru.

There are a few notable traits of shoujo heroines. One would be naivety such as in the case of Hikari from Special A, who is so naive, she can't fathom the concept of romance in her own life. Many shoujo heroine believe in the goodness of people and cannot think that others have bad intentions. There are quite a few shoujo heroine who will stand up for their friends, no matter how vile and selfish they really are, and defend them to the end.
Shoujo heroine tend to be the pure type with many outstanding qualities that bring out the goodness in some and make others feel completely dirty, but the shoujo series themselves will revolve around these endearing characters and show how they brighten up the world. It's truly a genre for making us believe that there are good people out there.

Shoujo tends to be a more lighthearted genre compared to some others. Many are full of exciting doki doki moments like Kimi ni Todoke where you can't help but cheer on Sawako through her transformation in school and get excited about her love life. It is a very lighthearted shoujo anime, but it still has you on the edge hoping that everything works out, but true to many shoujo anime, Sawako still retains her innocence believing that a rival in love is a commendable thing instead of taking it as a chance to best someone else. Then Kaichou wa Maid-sama is also a very lighthearted anime, but it still seems to capture many fans and has many moe moments!

Contrary to popular belief, shoujo does not always entail a high school life, though many do take place in high school and some may take place in middle school. Some may take place in college or further down the line as adults. Enjouji Maki is an example of a popular shoujo mangaka whose works tend to revolve around office ladies or young adults more so than high school girls.
Sub Categories

Despite what people think shoujo it, it can be fairly complex and does not solely consist of romance. There are many sub genres including fantasy, yaoi, magical girl, historical fiction, harem and ladies' comics. Yaoi is a very popular genre in shoujo, so much so that there are many jokes about girls liking yaoi in many different series across the board. Yaoi and shounen ai are very popular genres amongst girls, so it is no surprise that a large collection does exist as shoujo manga, but the love may continue for many girls as they become young adults so the genre does extend into the josei category as well.

Fantasy, supernatural, and historical fiction are common themes in shoujo, aside from the usual school life genre. A very popular series that has even been licensed in the USA is Tsuki no Shippo by Ueda Rinko which takes place at a time when ninja were believed to have existed and the main character is a kunoichi, Usagi who is supposed to marry another ninja. Despite having an aspect of romance, the series really revolves around personal growth than anything else, which goes to show you that shoujo isn't all romance.

Another notable subgenre of shoujo, almost as notable as yaoi, would be reverse harems. Yes, ladies get their own harems as well! These tend to have a singular female character surrounded by males who adore her. We have seen many become anime like Saiunkoku Monogatari, Yamato Nadeshiko Shichi Henge, and Ouran High School Host Club from manga, but many do come from visual novels as well like Amnesia, Diabolik Lovers, and Starry Sky. There are so many moe moments and scenes that drive you mad, it's worth watching at least once. Still, it is not a genre that is so plentiful in anime the way harems are. Reverse harems are more plentiful as otome games or manga, but the ones that are in animated form as still very fun to watch!

While the shoujo genre tends to be misconstrued as innocent at times, I want to make note that it is not as innocent as it may seem. That's when Ladies' Comics come into play. Once known for publishing josei, now Ladies' Comics publishes more steamy manga for the enjoyment of adolescent girls or office ladies. As a subgenre, this may be labeled as smut, involving something slightly more toned down than hentai, but it can be pretty graphic.

Although there may be aspects that are fairly serious in nature like rape, the mangaka will add in a budding romance between both parties making it seem more innocent and endearing than it really is. A popular mangaka who does just this is Shinjo Mayu whose works rarely seem to start off with mutual feelings. Of course, when these are made into anime, they are slightly toned down. Mitsu x Mitsu Drops (Honey x Honey Drops) by Minami Kanan is an OVA where you can get an idea of what may be included in the manga, but it won't give you anything graphic.

Now, a really popular subgenre of shoujo that draws in a large male audience would be the magical girl subgenre, but that isn't to say that all magical girl anime is also shoujo. Bishoujo Senshi Sailor Moon is a magical girl anime that is also shoujo for its character traits and the themes in the anime, while the magical girl anime Mahou Shoujo Madoka Magica is not a shoujo anime. A few other notable magical girl anime that are also shoujo would be Shugo Chara and Kamichama Karin whose heroines are very idealistic and pure in nature, and the plots are more lighthearted in content.

Publication of the original manga series is also a way to categorize a series into the selected genre, which may confuse some western audiences because of its notable difference from others in the same genre. An example would be the Deep Love series that is clearly more mature in content and not as idealistic as other shoujo manga, but because the manga is published in a shoujo magazine, it is is a shoujo manga.

When western audiences try to categorize anime as shoujo, many anime tend to be mislabeled as shoujo because often times, westerners will categorize anime that contain romance as shoujo such as Ah! My Goddess. Sometimes anime with generally female audiences will also be mislabeled as shoujo like Azumanga Daioh. Both of these anime are not shoujo, but they just happen to feature romance so it is a misconception that all romances are shoujo. It would be important to note that Gekkan Shoujo Nozaki-kun, an anime voted to be the funniest of 2014, is also an anime that can be misconstrued as shoujo, but it is actually a shounen anime.