The 11 year old Miyamoto Rebecca becomes the new teacher of a classroom which is full of weirdos. Despite her cute looks she's a little beast and can be pretty sarcastic and offensive. The school is not safe anymore now that she's in charge of a class and her students, Himeko, Ichijou, Rei and a white rabbit who took a liking to Rebecca help her to rough up the school and the neighbour-class with its teacher "ojiichan".
Join them now in their daily life full of gags and nonsense.
Class 1-C's teacher unexpectedly quits and a new replacement is quickly found: an eleven year old genius named Rebecca Miyamoto.
Becky is having trouble remembering the names of her students so refers to them by nicknames at first. Ultimately, she causes Kurumi to become depressed after calling her "plain".
Annoyed at Himeko's overactive nature, Becky rips off her ahoge which completely depletes her energy. The ahoge is transported off the planet by the aliens who then lose it. Becky must make a replacement ahoge for Himeko.
Becky unexpectedly announces there is to be a test the next day and the students of class 1-C don't know where to begin on studying. In the end they all decide to go to a sauna to try to study though not much gets done as far as academics is concerned.
All of the classes go to on a camping trip with teams consisting of four people. Kurumi, the one who planned the teams for her class, failed to remember to put her name on the list. Depressed about once again being forgotten, Becky tries to cheer her up.
Becky gets permission from the headmaster to have a personal research lab though getting the room to have it in is hard enough. Once finished, students start coming to her with their problems.
Class 1-C, due to Becky losing at Rock, Paper, Scissors, has to clean the school pool today. Also, Ichijou's little sister comes to school and causes some trouble.
Behoimi, the self-proclaimed magical girl from class 1-D, is starting to doubt her value compared to many of the other students who appear to have better characters. Becky tries to cheer her up, but doesn't succeed.
Becky is invited to an island on the southern tip of Japan to take part in an archeology expedition, though when she arrives she finds the students of her class already there.
Now that summer vacation is over, the students must present a project that they did over the break. Meanwhile, Behoimi and Media try to disarm a large amount of bombs that were set all over the school.
The girls of class 1-C find out that Sayaka Suzuki, also called "Rokugou", has been riding around with someone in a green convertible. Wanting to find out who's car it is, they enlist the help of Becky.
After the topic of dreams comes up, Becky discovers that she doesn't have any while all the other students seem to possess their own dreams for the future. When the aliens who have been watching Becky get a device that can read minds, they point it at Becky to find out what she is thinking. However, it hits Himeko instead and malfunctions leading to the members of class 1-C to be stuck in Himeko's dream world until they can wake her up.
The All-Japan Banchou League comes to Becky's school to have a battle with her, although they are much too powerful for her to take on alone. She must ask for the help of the students to defeat them.
Both the headmaster and the school chef go on vacation, which leaves Becky with no food to eat during lunch, since the bento her older sister made for her is inedible. She ends up relying on Kurumi's brother Shu from class 1-A to make her lunch, but when he takes a day off, what will she do then?
When on a school excursion, the bus of class 1-C ends up dangling on the edge of a cliff. There's not much they can do during this time but stay put and hope someone saves them.
The students of class 1-C notice that Ichijo is acting stranger than usual and try to investigate her whereabouts to discover what's the matter with her. Ultimately Ichijo finds out she's been "targeted" and requests help from the captain of the aliens.
The school festival has arrived and class 1-C decides to do a café called "Fighting Maid Café Momotsuki" which ends up being a very popular attraction. Becky, who originally had misgivings about the festival, finds ways to enjoy it throughout the day.
An inexperienced goddess of misfortune attaches a time bomb onto the forehead of Mesousa which is set to go off in a week, though after Media twists it a bit, it is then set for three hours. With such little time to live, Mesousa tries to find the goddess and see if she can help him. Meanwhile, Becky, Media and Behoimi try out various ways of disarming the bomb on a captive Akane.
A mysterious new virus called the Peach Moon Virus has infected the students of class 1-C and they are thus quarantined. Meanwhile, after Jijii contracts the virus and is quarantined, Becky tries to work with the students of class 1-D to try to find a solution.
The mushroom that attached itself to Himeko in the previous episode turns out to be an invading alien bent on conquering the Earth. There isn't much time left before its plan is carried out.
When Becky goes missing, and with a PTA meeting imminent, the students of class 1-C enlist the help of Akane Serizawa to impersonate Becky for the time being.
When the interview team from the show "Surprise Attack! The Homeroom Next Door" comes to Peach Moon and starts interviewing classes, Becky gets upset and tells her students she doesn't want to be filmed on television. Worried about her, her students try to figure out why she got upset.
It's the end of the year and it's starting to get colder. Eventually, unlucky things start happening to everyone and a snowstorm starts up outside due to a large comet on its way to Earth which will destroy all life.
The setting has changed to that of the Edo period. Bekiemon Miyamoto (Becky's supposed ancestor) has instituted a "Hauhau" tax which taxes anyone who cries. A faction rebellious of this new tax rises up and tries to fight against it.
Back to the events from episode 23, class 1-C finally sets out to defend the Earth only to discover the comet is in fact Ichijou's Festival featured in episode 17. After they get sucked into it, they must find the core in order to destroy it.
Despite it being December, it's very hot outside. The headmaster cancels afternoon classes so the students can have fun in a large water park which appears on the school grounds.