Rikka Takanashi (AKA "Dark Lord Shingan")
Chuunibyou, translating to "eighth grade syndrome", is a condition in which middle schoolers develop delusions of grandeur, frequently involving the belief that they have magical powers akin to anime or video game characters. Everyone's expected to go through some sort of chuunibyou phase, and to look back on it in embarrassment; surely many in the West can relate when looking back on their youth. Rikka is deeply invested in a chuunibyou delusion that she is "the Dark Lord Shingan", possessing a "Wicked Eye" and fighting with a sword. Of course, her "Wicked Eye" is actually just a gold colored contact lens worn under an eyepatch and her sword is actually just a parasol that's part of her gothic lolita fashion. While going through a chuunibyou phase is expected, Rikka is no longer an eighth grader, but in her first year of high school and still living her life as a chuunibyou. For the sake of indulging her chuunibyou interests, she founds the "Far East Magical Napping Society in Summer." She uses her elaborate fantasies as excuses for her difficulty functioning in the real world, refusing to clean her room so as not to interfere with the “magical properties” of her messy junk and too preoccupied to with her fantasies to study for her math exams without serious pushing and bribing from her friend and classmate Yuta.
Why is Rikka still so involved in these chuunibyou fantasies? The answer gets into mildly spoiler-y territory, but it’s an emotional one: it’s her way of coping with the death of her father. She couldn’t accept his death three years before the start of the series, and she came to believe that he’s still alive somewhere in the realm of the “Ethereal Horizon.” She formed her magical “Dark Lord Shingan” persona inspired by watching Yuta playing around in his “Dark Flame Master” persona. Chuunibyou for her wasn’t an unconscious coping mechanism, but a conscious choice, to try to insert some fun into a life that had taken a turn for the miserable. This was the start of her attraction to Yuta, which resumes at the start of the series when she and her older sister Touka move into an apartment above Yuta's and eventually turns into a romantic relationship over the course of the series (though her chuunibyou persona makes it hard for her to communicate her true feelings). Because she was always fully aware of her chuunibyou identity being a fantasy, she was able to keep it going long after most others her age would have given it up when faced with reality. Eventually, she does have to face her tragic reality, but her chuunibyou aspect remains a part of her, and with Yuta helping her, she’s able to use her fantasy of the “Ethereal Horizon” to finally say goodbye to her departed father. Chuunibyou may be embarrassing, but the show ultimately comes to the conclusion it’s still an aspect of ones’ self that’s never entirely grown out of.
Yuta Togashi (AKA "Dark Flame Master")
Chuunibyou demo Koi ga Shitai! may be primarily Rikka's story, but Yuta Togashi is the show's viewpoint character. Back in middle school, he was an obsessive chuunibyou, believing himself to be the “Dark Flame Master,” a fire-manipulating warrior preparing for the Mayan Apocalypse in 2012. Two years later, it is 2012, and Yuta is thoroughly embarrassed by his delusional past, hoping to live as a normal student at a high school far away from where any of his classmates in middle school could possibly find him. Yet the past still catches up to him when Rikka, as outlined above, re-enters his life and starts asking for the “Dark Flame Master." At the start of the series, he pines for the popular cheerleader Shinka Nibutani, whom he sees as a beacon of successful high school normality even though it turns out has more in common with him than he’d think. He agrees to join Rikka’s club mainly because Nibutani does. When he joins the club, however, he begins to develop feelings for Rikka, whom he senses is not just your typical delusional chuunibyou. Surrounded by the craziness of Rikka and her fellow chuunibyou Sanae, he tends to play the straight man in the series. Elements of his embarrassing past, however, turn out to come in handy in terms of speaking to the chuunibyou in their own language and keeping them occupied. He comes to grudgingly embrace his past in the process of reaching out to and helping the girl whom he loves. His shifting attitudes regarding his chuunibyou past and his friends' chuunibyou present reflects the mixed attitudes of the show as a whole, which manages to combine a comedic sense of embarrassment-based humor with a sense of sympathy and a weird nostalgia.
Shinka Nibutani (AKA "Morisummer")
Beautiful, smart, and popular, Shinka Nibutani is both a class rep and a cheerleader, someone who'd at first glance seem like one of the least likely candidates to get involved with the "Far East Magical Napping Society in Summer." At first, she seems to be drawn in out of sheer curiosity and a possible interest in Yuta. However, she's far more similar to Yuta than she'd wish to admit. Back in middle school, she was a seriously delusional chuunibyou blogging magical nonsense under the name of "Morisummer." When she snapped out of it, she developed a strong loathing for chuunibyou, deleted her blog, and moved away for a fresh start in high school. Little did she know that the chuunibyou duo of Rikka and Sanae had been saving and printing the entries in her blog and compiling it as a "spell book" called "Mabinogion." Shinka's true motivation for joining the club was to destroy the book, and she stays in the club for the sake of keeping the secret shame in her past under wraps. Sanae naively assumes she's lying about being the writer of the book, and deems her the "Fake Morisummer." However, against the odds the two of them end up becoming friends, a relationship which is developed into possibly more-than-friends territory in the follow-up OVA and the sequel series.
Sanae Dekomori (AKA "Mjolnir Maul")
Sanae Dekomori was not a character in Torako's light novels but rather an original creation for the anime, and she's a memorable one. Sanae's the youngest member of the "Far East Magical Napping Society in Summer," only in middle school. As such her chuunibyou persona is more age appropriate, and while she's super hyperactive, swinging around her long pigtails like a weapon pretending to be wielding the hammer of Thor, she's actually very high functioning compared to Rikka. Sanae might be a chuunibyou, but she's also at the top of her class with advanced skills in mathematics. Furthermore, while she's dedicated to her chuunibyou persona to the point where the possibility of having to give it up has her heartbroken, she has a self-awareness that none of this is real. In that light, being "Mjolnir Maul" seems to be more like an advanced form of LARPing, a way for a genius kid with a wealthy family and a lot of free time to enjoy herself and make everyday life more exciting. The lengths she'll go for her game may embarrass her some day, but as long as she has the self-awareness to know it's just a game and it doesn't interfere with her ability to function in day-to-day life, can it really be considered a problem?
Kumin Tsuyuri
Like Dekomori, Kumin is an anime-only character. Unlike Dekomori, she doesn't add much to the main plot or themes of the anime. She's mostly tangential to the main action, a heavy sleeper wanting to start a napping club and, when napping gets incorporated into the extended name of the "Far East Magical Napping Society in Summer," lying around on the sidelines, interested in the chuunibyou without being one herself. Her big time to shine is in the final episode of the first series, in which she delivers an important message on behalf of "Dark Lord Shingan".