Mahjong Oneshot included in the same volume as Death Pie, another longer mahjong manga by Shimamoto Kazuhiko.Related: http://mangapark.com/search?q=death-pie

17 year old exemplary student Bae Sugu lives alone with his father, the vice principal of his school. Weighed down by his father's expectations, Sugu has to hide his one true passion: swimsuits. He does not know where it comes from, but his passion is pure and genuine - and often misunderstood. But one day, when Sugu is secretly taking pictures of swimsuits by the pool, he is caught by his homeroom teacher who forces him into something ridiculous. Can Sugu find something to get out of the standstill his life has come to? Can his heart beat again? Webtoon from Naver

From Hells_Castle:

Tashiro Mizuho is your typical middle school teen... except for the fact that he is a cross-dresser! When an upper-classman's sister transfers into his class after living abroad, what awaits Mizuho in the future?

Brothers Akira and Suguru love to cross-dress and have no qualms about showing their panties, something their neighbor Hiro tries to prevent.

Collection of various oneshots, including Katou Shinkichi’s debut work, which was originally published on November 22, 1990 in Weekly Morning.

For high school girls there are some "battle days", for example Valentine's Day, Christmas, and...

Marimo has a job to do... but it's too cold and she doesn't want to leave the kotatsu.

Short stories all related through a common medium: Eggplant.

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.

Wakaba Chiharu is a fujoshi, but hides it from her friends. She fantasizes about male classmates being intimate and uses them for her manuscripts. But somebody is interfering with her daydreams...

A high school girls' portball (simplified version of basketball) team plays against the boys' team to fight for the right to exist!

Set in feudal Japan, Sorano is often mistaken for a girl, and he is saved one day by Iori from some pushy guys; the two hang out together the following day.

Really short like 4 pages

44 years old and still unmarried, construction worker Kurosawa wants nothing more than a little respect from his co-workers...and some popularity wouldn't hurt either. Unfortunately, Kurosawa's awkwardness and lack of social aptitude causes any attempts he makes to that effect to fail miserably time and again. But one day, his already bad luck takes a sudden turn for the worse.

From Rayns&Lele Scans:

No matter how you look at it, Kamijou is an average guy. On the other hand, his ex-childhood friend, Aikawa Itasu, is a popular and intelligent girl. Believing his childhood friend to be in a whole other world than himself, he starts putting distance between them...
Until one day, Kamijou’s cat, Peace, sneaks off and visits Aikawa. The two of them starts talking again. What's Aikawa's motive for feeding Peace? And... will they end up reconnecting?

Palepoli goes beyond the framework of standard four-panel manga and views its structure in new ways. Actually, Furuya knew nothing of conventional manga styles and methods when he started Palepoli. As a result, he created something that bore little similarity to other manga. Furuya notes that he selects his subject matter and methods with clear and precise intentions.

A portion of Palepoli was featured in Secret Comics Japan.

Quoted from 4dawgz (the scanlator)-
"So there's a magazine called Gelatin where various manga artists are given some coloring crayons and then told to draw whatever they want in full color. The plot for this is about a guy and a girl who go on a mission to retrieve a pair of shorts from an island... aaaaand that's it. All you'll find is a nice slice-of-life story and lovely colored pages."

Sugano Ikkei is a typical teenager at his high school and lives with his older brother Hyakkei who is an editor at a publishing company. Hyakkei is in charge of several artists and writers and his job is to support them in anyway possible. However, he broke his leg and is unable to leave the hospital for a week and he has a very important meeting with a very shy writer named Tokito Aona which has taken months to get a face to face meeting. As they look really alike, he asks Ikkei to dress up as him and go as Hyakkei. The meeting goes well without her knowing the truth, but Ikkei is forced to go to another meeting with Fujimaki Misuzu, an artist moving to Tokyo in order to continue working. To his surprise, both girls, Tokito and Fujimaki, are in the same class as he. Now he has to juggle being Hyakkei as an editor to the two girls as well as be their classmates as Ikkei, and do all this without letting out the secret that he is the same person.

After a four-year absence, Ishida Kotori (QP) returns to the city where even his face instills fear amongst the locals. Trying desperately to move away from his once violent past and live an honest life, former classmate and now high profile gang member, Azuma Ryou, has other plans for QP's future...

QP: Soul of Violence is written by Takahashi Hiroshi and set within the same universe as his other works, Crows and Worst.

4-koma manga

One day, an un-named ordinary high school girl (her name is left to your imagination), meets Cheko, a maid sent forth from a village of maids. Cheko the maid can melt, fly, remove her head and violate physics.

Surrounding the "ordinary high school girl" and her strange little maid are yuki-onna's who hate cold, a cute squid that can speak, moe yankees, tsundere maid assasins, ecchi lesbian teachers, trap yuki-otoko's, gentlemanly yakuza and many more.