The continent of Halkeginia is tumultuous--a place where the various kingdoms, princedoms, dukedoms, and fiefdoms strive against each other to expand their domains. They nobility scheme and plot among themselves to gain influence to their lieges or to even foreign lieges. In the middle of Halkeginia is the small but important kingdom of Tristein. The most notable fact about this kingdom is the Tristein Academy of Magic where nobility from all over the world come to study magic so they can become magi. Although friendships will form across national boundaries at this school, will they survive the politics and games of the world at large once they leave?

Louise is a student at Tristein Magical Academy. She is known to be quite a screw up when it comes to her magic. One day, a ceremony takes place where each student is to call forth a being or entity that will become his or her familiar. For Louise, her familiar comes in the form of a boy named Hiraga Saito. Somehow, he managed to get transported from his world into hers, and shortly after became her familiar.

Ashihara Chihiro is a regular high school student. One day a man came to her and told her that she's actually a princess from another country in another dimension. Chihiro later found out that it was true, and in fact her own best friend and teacher were actually her guardians! Her country has been taken over by Raja, who is now king. Chihiro and her guardians come back to that dimension to take back their country. In her quest, Chihiro met other guardians and warriors who were willing to help her achieve her goal.

From Manga Jouhou:
Takashi Sone is living on his own while he is attending college. Out of the blue, his parents tell him that his sister, Mafuyu, is moving in to live with him and that she will be attending a high school in his area.
When she arrives, he finds out that she was kicked out of her old school for getting caught making out with another girl. Soon afterwards, the other girl arrives, having thrown away everything she owns in order to run away and live with Mafuyu.

Volume 11 has a unreleated 2 chapter story at the end called Frills

Tsukiko has joined the academy's archery club. As she practices for the summer competition, she also solves the problems between her teammates (Homare Kanakubo, Ryunosuke Miyaji, and Azusa Kinose) simultaneously

From Houkago Scanlations:

Shiki threw everything away for the sake of revenge. But at the new school where she disguises herself as a male, she meets 4 popular rich guys... Haru (spring) the prince, Natsu (summer) the bishounen, Aki (autumn) the womanizer, and Fuyu (winter) the cold-hearted genius.

What awaits Shiki? And will she get her revenge...?

The main character Haruto who has the marking of a supreme king, unknowingly opened and entered the gate to the world of divine spirits. There he meets Feilen-kamisama who makes a contract with Haruto for an unexpected reason. Later Raika, nation of thunder, comes along and makes things more confusing for Haruto! What happens after this? A riot that flips his life upside down… or flat to the ground… NOTE: On hiatus

Teishu Academy is a school for the wealthy, high classed students that the upperclassmen can offer. Being at such high class the Socie, a school group that is almost like security, keeps a lookout for anyone who tries to bring in any portion of lower class culture. An example of this is an anime based keychain, which is a Rank 1 unacceptable item on campus ground. Those who break the rules are then crucified and called "Criminaes" and are set to be shamed by the public. Due to an increase in the number of such Criminaes, Hajime, the Shvarie du la Fleur of the Socie, has announced that the Socie will conduct unscheduled searches through each student's bag. A new student, Rentarou, is shocked at this since he accidentally had anime related material hidden inside his bag. He desperately tries to run from the Socie, but gets caught by the Socie leader herself! But instead of a severe punishment, the Socie leader, Ayako, decides to have Rentarou join her in creating a doujin game.

Spinoff series of Kanojo ga Flag wo Oraretara

From Manga-Heaven:

Eitaro is hooked to the erotic chats... Someone steals Sakuko's lingerie... Ai is determined to lose her virginity... Everybody is hooked on love... or is it to sex?!

An erotic manga by Kyo Hatsuki following the trials and sexual triumphs of the main character. The story travels from - "Will he ever get laid?" to - "Will he ever get a steady girlfriend?" to - "Will he ever learn to keep it in his pants?!"

Koi to Senkyo to Chocolate follows the protagonist Yuuki Oojima, who attends Private Takafuji Academy, a large school with over 6,000 students. Yuuki is a member of the food research club, along with seven others, including his childhood friend Chisato Sumiyoshi. The members leisurely spend their time in the club not doing much activities. When the election of the next student council president comes up, the front runner Satsuki Shinonome proposes that clubs that have no merit should be sorted out and abolished. The food research club seeks advice from the current student council president Yakumo Mori, who suggests Yuuki run in the election as an opposing candidate. Yuuki learns about the issues facing the school and decides to run in the election.

Adaptation of Satsuki's route.

From Yen Press:
A mysterious illness is spreading rapidly through the halls of Fujimi High School. In a matter of hours, the campus is transformed from a place of learning into a hive of nightmares, as the infected students collapse and are reborn as flesh-hungry zombies! Only a handful of students escape the initial outbreak — among them Takashi Komuro and his childhood friend, Rei. He manages to protect Rei from the initial onslaught, but how long can Takashi and the other students hope to survive when the whole school – maybe the whole town — is out for their blood?!

Story about a salaryman who was going to get married soon but his bride runs away with another guy. His life sucks. He had to borrow a lot of money to buy a new house for his married life but ended up with nothing. Then his boss offered a solution: make his house into a girls' dormitory for female employees in the company. His new life begins here.

In this city, there is a legendary thief. An eccentric thief who lived down through the generations. A story that's told for generations. His name is Mugensai Ishikawa.

Kanadegumi follows a girl named Miyabi Neko and her interactions with five attractive young men. The story takes place in Tokyo and centers on an imperial opera company named Kanadegumi.

From Phoenix Serenade Scans:

A story set in the Taisho Era. Meet Miyabi Neko, a girl with bad luck from a small place called Izumo, who aspires to become an actress by joining the capital's most popular acting group Hanagumi! And after some hard work, she was finally accepted into Hanagumi! But, when she reaches the capital, there is some disturbing news. Apparently, she is not to join HANAgumi, but the capital's music group KANADEgumi! And she meets some strange but handsome young men on the way? What is Neko's life going to be like in the capital?!

The manga follows the story of 16-year-old Mana on an adventure through the Aquarian Age. A sixteen year old girl, Mana returns to her hometown to reunite with her childhood friend after having been gone for seven years. But her friend, Kaname, seems to have changed too while they've been apart. Mana's re-emergence soon sets off a series of events that alters the lives of Kaname and his best friend, Naoya. Classmates Isshin and Tsukasa, as well as their teacher Tomonori, find themselves drawn in as well. Soon, they all discover that they have a part to play in the "Aquarian Age" - a war that has been secretly raging for thousands of years. Now the future of the world depends on one girl and her destiny.

Taglines:

Do you want to know this transfer student's secret?

Are you going to fall in love with the world's most cheerful little girl?

Jutten! is about a boy who goes to his first day of high school, thinking it'll be full of awesome (pervy) meetings with sexy girls and whatnot, but instead has a lot of bad luck and gets peed on by a dog--amongst other things. A girl who uses her bike to drive over his ass sorta helps him and gives him a handkerchief with a 10 yen coin in it (hence the the serie's title) and ... very plausible stuff happens afterwards.

From Shoujo Manga Maniac: Nao, a first year at jr.high school, decide to enter Seisei Gakuen in order to follow the person she fell in love with at first sight! Once coming there she find out that her "Onii-chan", the nick name she give to her beloved Wada Yoshikuni, is part of K.I.S.S....but what is K.I.S.S?

Karugasaki Tora decided to repeat a grade and turn into a delinquent just so he could be popular, on his best friends advice. However, his plan backfired and nobody talks to him in his new classroom. The only thing he can look forward to is seeing the cute girl sitting next to him, but after trying to talk to her she immediately kicked him and threw him out the window. Later the same day, though, he saved her and a little girl from being hit by a truck. No longer able to avoid him, the girl reveals that she's a ghost playing a shinigami's game. She must get the boy she likes to return her feelings at times given by a pair of hourglasses so she can return to life, or fail and be sent to hell together. Unfortunately, her feelings have awakened for Karugasaki...

Rewrite is set in the fictional city Kazamatsuri where treeplanting and afforestation have caused the city to become overgrown with trees and flowers in much the same way that other cities are filled by buildings. However, while most of the city appears to be rural, there are many traditional city elements as well. While set in a modern setting, the city also gives off a strange sense of nostalgia. The basis of the story is set in a high school setting.