Nanami transfers to St. Marivel (Mary Bell) High School from America as she looks for her childhood friend, Kotaro. In a school where the ratio of male students to female students is 1:20 respectively, Nanami gets involved in a conflict with a male student who is almost twice her size. As Nanami was about to engage in battle, she catches a glimpse of Kotaro and stops, allowing the male student to grab hold of her! How will she get out of this situation?

From Wingtip Cafe:

In Edo (ancient Japan), an oiran (high-class courtesan) joined a robber gang that stole from the rich and gave to the poor. Together, they battled against the enemy who used ‘Eleki’ (electric gadgetry and dolls) as weapons.

Teppei Arima is a second-year high school student who lost both of his parents in a traffic accident on their way home from a family trip. His grandfather, Isshin Arima, happens to wield the puppet strings in Japan’s vast economy and demands that Teppei becomes his successor as the head of the Arima Group. To prepare for his debut into high society, Teppei enrolls in an elite academy for the scions of the rich and powerful.

Mizuho can't believe his ears when Grandpa's will is read out. Grandpa's final wish is for Mizuho to attend the same academy as Mizuho's mother. The catch is it's an all-girls school. With the help of his friend Mariya however, he gets a makeover good enough to fool everyone at the academy.

Inukai Shirou a male high-school student leading his life when suddenly his dog Mashiro turns into a human girl and now he must satisfy her wants or face the consequences.

Hina moves back to her old home town only to find that the high school is run by two opposing factions, and students identify themselves based on the color of their school uniforms: Black for the followers of the ostentatious, violent Nishizaki, and white for the followers of the misanthropic, clean-freak Isshiki. And, as if it wasn't complicated enough, there are the "grays," who wear their own clothing, deciding to be their own people. Hina finds herself stuck between the leaders of the two factions, and it seems to be turning violent.

Also contains a oneshot: 3 Days

[From AT-Translations]:

Based on an ero-game, Prism Palette is Peach-Pit’s (famous for DearS, Zombie Loan, Rozen Maiden and assorted other manga) first publication. It follows the main character, Masaki Shirai, as he spends his days at school, surrounded by beautiful girls.

From Intercross & Shoujo Crusade:

1-3. Sorairo Koiiro
Sora somehow ended up in a science class with all boys. Now, she's going to pitch in and help them enjoy school life by showing them her Girl Spirit!!

4. Sakurairo Koiiro

5. Sore demo Yappari Kimi ga Suki
The energetic and cute Rin is actually an otaku! Unexpectedly, she meets a 3-dimensional boy with the same looks as her beloved, Chris-sama! Otaku love in full bloom.

As a boy, Taishi saved a tiny chick (as in an actual bird) that was being bullied by its brothers and sisters. And now it’s grown up into a hot girl who wants to cater to his every whim! Did we mention she lays eggs, too?

Itsuki Minamori has fallen asleep in class and dreams about a girl from his past. He is awakened by Haruna a girl who apparently has a crush on him, but her friend Chihaya Yuuki tells her to stay away from this boy. He explains that he's spent his life being followed by evil ghosts and during the exposition, another one shows up.

Rin, Nerine, Itsuki, and Mayumi find a strange watch that transports them back in time, where they met Forbesii before he is married and has Nerine. While he is engaged to Ai, his maid, Sage, is also in love with him, causing a love triangle.

A 4-panel comic strip crossover series featuring characters from both "History's Strongest Disciple Kenichi" and "Skill Hunter Tekuni".

Tayutama Kiss on my Deity centers on Yuuri Mito, a student at the Sousei Academy and the only son of the man who runs the Yachimata shrine. At Yachimata, there is a legend of a deity named Tayutayu-sama who protected the area, but this deity and other so-called “Tayutai” have been lost in time. Mito and his friends discover a relic on the school grounds with mysterious patterns on them. Then, at the opening ceremony of the new school year, an equally mysterious girl named Mashiro appears before Mito. Mashiro is somehow tied to the relic and the legend of Tayutayu-sama… [Mangaupdates]

The story revolves around Taiga, who doesn't have memories from further back than two years ago when his parents died in an accident. He lives with his sister, Tsubame, whom he finds out is from outer space with the job of protecting him as he possesses the Origin Heart.

What would you do if a tiger skin bikini-clad alien followed you to school every day? Poor Ataru's life has never returned to normal since volatile extraterrestrial princess Lum fell for him. Now an excruciatingly wealthy and genteel rival, Mendo, adds to Ataru's torment. Not to mention an unending stream of extraordinary classroom visitors and educational materials including incompetent cherry blossom spirits, a legendary nightmare-eating tapir, and a fourth-dimensional camera that breeches alternate realities.

Note: In 1981, this series received the Shogakukan Manga Award.
Won the 18th Seiun Award for Best Comic (1987).

The new student by the name of Masato Takasaka transfers to a school full of delinquents which is currently undergoing a battle between the various student activities committees. His fleeting expectations of a delicate and loving school girls and a peaceful school life go out the window the moment he meets the declared queen of the school Onizuka . What will happen to the school life he dreams of in this romantic/comedy of two unlikely partners in school full of delinquents?

The onsen world lies beneath our own has spirits which can only be seen by those who truly love onsen (japanese baths). After his grandfather dies, a japanese student summons one of these spirits...

Innocent country boy Oyamada Kouta transfers to a big city high school in his freshman year, and from day one, his life enters a world of crazy. First, a beautiful second-year student named Chizuru professes her love to him, then reveals that she is in fact a fox spirit. Frisky and flirty, her suggestive teasing of naive Kouta in front of his classmates embarrasses him to no end.

If that wasn’t enough, a gorgeous wolf spirit named Nozomu suddenly transfers to Kouta’s class and decides she wants the hapless country boy for herself. As fox girl and wolf girl vie for his heart, does Kouta have any say in this?

From Del Rey:

The young ninja Kagetora has been given a great honor - to serve a renowned family of skilled martial artists. But on arrival, he's handed a challenging assignment: teach the heir to the dynasty, the charming but clumsy Yuki, the deft moves of self-defense and combat. For a ninja like Kagetora, to fall in love with his master is a betrayal of his duty, the ultimate dishonor, and strictly forbidden. Can Kagetora help Yuki overcome her ungainly nature… or will he be overcome by his growing feelings?

From Aerandria Scans:

Kei is a girl who's only interested in other girls! However, tricked by her mother, she enrolled in an all boys school, thinking that she'd be able to make her high school debut at a co-ed school. To normal girls, being surrounded with hot guys at an all boys school might be heaven, but to Kei, this is hell! What is Kei to do at this place without any other girls, where she has to try her best to keep her real identity a secret?!