A series in Young Magazine and Young Magazine the 3rd, where authors write the 100th chapter of a series without writing chapters 1-99 first.
1. Offside Trap by Kumeta Kouji
2. Tabete Kara no o Tanoshimi da yo! by Ooima Yoshitoki
3. Bravery Saga by Yoshimoto Masume
4. BattleSexer SEISHIRO by Kubo Yasuhisa
5. Shin Oni-den Nagugowainega by Oshikiri Rensuke
6. Kantan Z ~Kanzen Tantei Kanta, Saisho de Saigo no Jiken~ by Suzuki Nakaba
7. Sasa ni Negai o★ by Yamamoto Souichirou
8. BOWWOW Providence ―Isetsu Hakkenden― by Segawa Masaki
9. Bari Uma Shokudou Kirishima!! by Seo Kouji
10. Nie Miko no Touya by Yoshimura Kana

From MangaHelpers:
People have been created that are human-animal hybrids, and powerful businesses bet on the outcome of their duels. College student Nomoto Yuuya's casual acquaintances ask him to drive them around to pick up girls one day, which he soon finds out means by force. The girl they kidnap is an animal-human hybrid named Hitomi, who slaughters all of them except Yuuya. Hitomi is a honey badger, which has been called the most fearless of all animals. Now Hitomi is assigned to stay with Yuuya, for his protection.

17-year-old Nowaki Asunaro has been forsaken by fortune since his birth. Every step he takes, bad luck awaits, whether it takes the shape of a falling bucket of water on his head or being blamed for crimes he never committed. Even for an exceptionally unlucky fellow like him, he still hopes to become friends with the love of his life: Hashihime Banri. The only problem lies in the fact that every time he almost gets close to her, his lack of luck blocks the way.

On one typical day for him, filled with unfortunate accidents, he ends up having to protect himself from the rain in a forsaken and dilapidated temple. He becomes feverish from cold and hunger, but in desperation, he prays to the gods that he survive this day and become friends with Banri. Lo and behold, it seems like he accidentally summoned a God(?). Will this accident bring him the luck he never had?

From the Outerworld Scans website:

Tetsushi (a 5th grader delinquent who rules over the students of Jouin elementary), Ryuuchin (Tetsushi's right hand man) and Tsuda (their sometimes-ally), are known to everyone in town as the "three evil prankster kings."

In a creepy pharmacy located out-of-town, the boys meet an old man who bestows a strange and other-worldly power upon them. Soon after, our 3 young pranksters find themselves battling a variety of ghosts and demons...!?

Everything in this world is my enemy. This kind of world is worthless. A boy, who is called a demon with no human heart, breathes, lives and imagines. But what is the pounding in his heart when he heard he is going to save the world? That’s not his wish, though…

As a child, Kasama Ryuuji watched his parents killed before his eyes by the rival, Yazuka gang. As a teenager, he finds the woman who raised him after the death of his parents, raped and murdered by the same gang. With the lost of his loved ones, Ryuuji wants nothing more to do with the Yazuka. When everything seem lost, the kind and caring, Araki, who claims to be the brother of his adoptive mother appears. Ryuuji develops a special bond with Araki but how will Ryuuji react when he learns that Araki, in fact, is the only surviving member of the Kasama gang, who has devoted his life to protecting Ryuuji. Will Araki-san, the dragon, be able to keep Ryuuji safe, or will his enemies use the young man as a pawn against him? (from MegKF by Rogue11)

NOTE: Each Hana to Ryuu Soushuuhen volume compiles 4 doujinshi volumes.

Hana to Ryuu Soushuuhen 1 (1998)
#1 Chiri Isogu Hana
#2 Hei no Naka
#3 Ryuu no Tsume
#4 Futatsu no Saikai

Hana to Ryuu Soushuuhen 2 (2000)
#5 Shinjitsu wa Yami no Naka
#6 Yomigaeru Akumu
#7 Mienai Tobira
#8 Ryuu wo Karu Mono

Hana to Ryuu Soushuuhen 3 (2003)
#9 Hebi no Rasen
#10 Kienu Juujika
#11 Karamiau Kizuna
#12 Tsuki ga Michiru Toki

Hana to Ryuu Soushuuhen 4 (2006)
#13 Kaiko to Zouo
#14 Kioku no Kakusei
#15 Aizou no Yukue
#16 Hebi no Doukoku

Hana to Ryuu Soushuuhen 5 (2007)
#17 Ai to Yami no Hazama de
#18 Yume no Mahoroba
#19 Matoitsuku Bourei
#20 Tamashii no Doukoku

#21 Tomurai no Hana (2009)
#22 Kibou no Akari (2009)
#23 Tabidachi (2010)

From MangaHelpers:

Another version of the story of the Inspectors and Enforcers from Psycho-Pass, but this time in chibi style! All of the main characters are now in chibi form, and are attending a "Psycho-Pass Academy," which is basically a chibi-fied version of the scenario of the original series. New student Tsunemori and her classmates will use their Dominators to keep their school's peace! [tethysdust]

From the author of Necromancer.

Collection of short stories.

Doraemon, a cat shaped robot which came from the 22nd century in the future, goes back in time in order to help Nobita, a below average lazy kid, to make his life less miserable and improve his descendent's life. With many of Doreamon's gadgets from the future, Nobita's life will never be the same.

Note: It was awarded the first Shogakukan Manga Award for children's manga in 1982 and also won the Tezuka Osamu Cultural Grand Prize in 1997.

From MangaHelpers:
Tonight, Natsuo loses his virginity. His partner? Her name is Rui and he just met her today after school. She's the one that brought up this whole situation, stating that she wanted to simply gain the knowledge about sex. She does not want to start a relationship, nor does she care about Natsuo.
Afterwards, Natsuo feels guilty for losing his virginity to a girl he doesn't even particularly like. Mostly, it makes him feel like he betrayed his crush to his high school teacher: Hina. A quirky love triangle story unfolds as Natsuo, Rui, and Hina all end up becoming part of the same family.

Everyone on the Clockwork Planet considers Naoto Miura a machinery nut. Every moment of every day, he has his mind on gears and his hands tinkering with delicate mechanical motors, but nobody understand how he can hear and feel gears in operation, even from a long distance away. Then one day, a clockwork maiden falls from the sky, presaging events that would shake the whole world.

After Ryou's father remarries, he's not sure what to do with three new brothers and a stepmother at the age of 19. As he comes to appreciate his happy new home and family the glue holding them together starts to come undone. How will these four brothers weather tragedy after tragedy and stay together?

Japan is now the 51st state of the U.S.A..
The isle of Neon, located near Japan, is the only place where prostitution and gambling are legal. There, Italian Mafia, Chinese Triad and Yakuza fight each other to gain the control of casinos and brothels.

Iori Shijima, an ordinary high school student blessed with a good, common life. He has a cute childhood friend, lots of friends he can rely on, and a nice and beautiful mother. Additionally, his grades are good and he has a solid future plan. However, one day "transcendent beings" called ĀTRAIL appear on Earth, and Iori's everyday live crumbles as he learns about the secrets of another world and the meaning to his own existence.

The accompanying 4koma for Accel World.

From Yen Press:
No matter how much the times change, bullied kids aren’t going anywhere. And fat junior high school student Haruyuki is one of them. But one day, Haruyuki encounters Kuroyukihime, the most beautiful and elegant girl at school, who gives him a mysterious program: “Brain Burst”…and the secret of the “Accelerated World.” He may be at the bottom of the food chain at school, but Haruyuki and his destiny begin to “accelerate” with incredible speed in the virtual realm as he aims for the top.

There is an inn that you can visit where you'll find old things you thought were lost forever.

From The Zero Alliance:

Asagi is an exorcist with a tragic past.
One day, an encounter with a certain ayakashi causes him to recall that tragic past…

A collection of stories:

1. Toshokan no Hime-chan (The Princess of the Library)

6. Nakimushi Ouji-sama (The Crybaby Prince)

From Canis Major Scanlations:

When the President got into an accident, Shirotani Tadaomi met Kurose. On their very first meeting, Kurose could tell right away that Shirotani is Mysophobic and said that it's pretty bad while suggesting it would be better to consult a doctor about it. Shirotani was left perturbed by the encounter. Who is Kurose? And how was he able to tell Shirotani's condition?

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"Mirror" - Artbook