Hito Natsu no Kids Game (ひと夏のKIDSゲーム Hito Natsu no KIDS Gēmu) is a short, debut manga work by Ken Akamatsu, the creator of Love Hina. The manga was published on September issue of Kodansha’s Magazine Fresh on September 10, 1993. Ken Akamatsu later received Kodansha’s "Freshman Manga Award" (Japanese: 新人漫画賞/少年マガジン新人賞) and Special Jury Award (Japanese: 審査員特別賞) for this work.The manga was re-published on 20 May 2001.

(Description taken from Wikipedia)

Mamoru is a Nishiarai game player who has switched to a first-class powerful new high school named Hijiri Gakuen Koukou. There he met with a group of eccentric game lovers who call themselves Dennou Kenkyubu, he accidentally joined and had to undergo a variety of events and adventures with them.

Story of Hatta Shuuji's encounter with problem-child and popular model Haru. Incidentally Shuuji is the childhood friend and ex-housekeeper of Maruyama Mie.

Spin off of Hitsugi no Chaika. Takes place in high school.

From Winter Translations:

This is a story about a pair of twins who're, undeniably very different from one another. Big brother Shuuya and little brother Yuuta are basically light and shadow...

Rika is known to be a cheerful girl, but is that her real self?

From Loveless' Site:

Amidst the crowds in Asakusa district, Tokyo, a young man is assaulted by a group of bandits. When a red-haired stranger comes to his rescue, Suoh falls in love at first sight, but all's fair in love and war.

Li Xao Yao left S.W.A.T to become an ordinary security guard, while working, he happened to enter the VIP room and found Lin Wan Er still in the middle of changing, as revenge, she took him on a ride and kicked him out of the car. After hours of walking, Li Xao Yao finally managed to get back home just to be kicked out of the house. He then got an offer from his previous supervisor to become the bodyguard of the Tian Xi group ceo's daughter both in game and in reality. But unknown to Li Xao Yao the girl was actually...

Madam Misa dies mysteriously at the Saturday Night Club. Soon after her death, her young handsome and broke host Hideo opens a similar looking "Host" Club of his own. Where did the money come from? Did Hideo have something to do with Madam Misa's death?

From Sura's Place: Regarding R is the stories of four women who are friends. All four women have problems of their own. One just wants to be loved. One wants to find what she is living for. One wants to have a good career. One wants to just move on. While they are "friends," they don't always get along and you will get to see their dark sides.

Hime Arikawa is a high school boy with a huge debt, and he is saved by the girls of his school's student council after being chased down by yakuza debt collectors. The student council agrees to pay off his debt if he'll join the student council and spend his high school life cross-dressing.

Mi Ju, the most beautiful cosmetic model of CF, and her school friend Yu Jin, are thrown to the past where at that time people's opinion about beautiful woman are different from nowadays. Mi Ju who is loved by her beauty and body height, in those times was considered as 'ugly woman'. They must find ways to get back to the future if they don't want to live in those times forever.

Five years ago, Hokazono Akari died in an accident. Now 23 years old, her boyfriend and childhood friend Shiki Daichi still hasn’t found closure. While he chases after memories of her on the earth below, she uses every tool at her disposal in heaven above to force him to forget.

Long ago, in the far reaches of space, there existed a world as pure and blue as the Earth. And on this world, there lived two "Queens" with the power to control it. When the world is thrown into chaos by one of those queens, a young boy and a young girl must stand up to challenge her for the sake of protecting all that they hold dear.

Note: TSP is using the tankobon chapter numbering (where ch. 12.5 is ch. 15-17 in the magazine raws) compared to groups who previously used the magazine raws.

In a certain village, in a certain cave, lies a young girl that has been sacrificed. A certain mysterious man comes to her rescue...

Another series based in the original world of Yurara no Tsuki.

By all appearances, Sakura and her friends are normal, albeit sheltered junior high school girls who enjoy talking about love and walking home from school together. However, they also happen to inhabit a strange and supernatural world populated by mysterious, gigantic beings and unusual plant and animal life. Amid their peaceful lives, Sakura becomes very interested in something only alluded to exist in an old book: dicks.

1. The Circle
All social connections fall into circles, some circles intersect, and some people can never connect. Captain Tachikawa wants to be closer to talented amateur Furuda, but it's surprisingly difficult.

2. The Box
After seeing the friend he's loved for ten years be swept up in an out-of-the-blue romance, Andou's more than a little heartbroken. Then in steps the freakishly tall Higa, a first year at the university, to pick up the pieces... if only Andou actually wanted him too.

3. Blood Hope
A man(Hisae Kai) living with his daughter and grandchild finds a mysterious book and releases a demon(Hakuou). That demon offers to grant him one wish, but for a price...

4. Blood Trap
The story of Blood Hope continues with Hisae Kai, his daughter, his granddaughter, and Hakuou - a demon - living peacefully together. This peace is interrupted by a heavenly messenger sent to seal Hakuou, and Hisae must move to protect the ones he loves from this meddlesome spirit.

5. Blood Chip
Hisae Kai, his family, and the demon, Hakuou, still live together blissfully. One morning, Hisae gets fed up with Hakuou's overflowing pottery works that are blocking Hisae's workspace and demands that he removes them. During the cleanup, Hisae is attacked by a strange creature and Hakuou must protect him.

6. Akuma to Issho
A short one shot, more like a small extra, to the Blood- Hope, Trap, and Chip series of one-shots.

7. The Circle Extras

From Hearty Thrills:

Meguna Hirasawa has confessed 5000 times in total to her 10 year long crush Ayumu and in turn, received 5000 rejections. But that won't stop her. In fact, Meguna is retiring from simple confessions and moving to a whole new level. That being said, Meguna is ready to dive straight into seduction! Wait, the first thing she does is smash her lips into Ayumu's face for a bloody kiss?! Will her pestering finally allow her to capture Ayumu's heart? Or will this desperate girl's hard work be in vain?

From Chibi Manga:

You can't compare me to the perfect sister! I don't know any sister but when I entered in a far away high school something happened...