Ikuo Ryuuzaki and Danno Tatsuya are 2 orphaned boys who were looked after by a person they called 'sensei'. Following their sensei's brutal murder, the two vow to hunt down the killers and the police officers who neglected to properly investigate the case.

15 years later, Ryuuzaki is a police detective and Tatsuya has become the leader of a group of mobsters. Helping each other out behind the scenes, they strive to rise to the tops of their respective fields so that they may exact their vengeance.

From Aerandria Scans:

The beautiful singer Lucille and his orchestra invite you to the city of fear where puppets hunt down humans. The puppets are playing an oratorio of magic and illusions!

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This manga also features the unrelated short story Camelot Garden in vol. 5.

Quinta is an infamous grand witch who has lived over 300 years and is known for her cruelty and killing other witches. She's shrouded in mystery and secrets, but the truth is, she's actually only 16 years old. In an unexpected turn of events, Quinta becomes a bodyguard for Nestor Gilroy, a renowned professor with 5 PhDs, who is being hunted down for his unpublished research. Together, Nestor, Quinta, and her animal companion Feeyo embark on a journey in order to have Nestor's results published.

From MangaHelpers:
High-schooler Matsuzaka Satou has a reputation for being easy, but one day her lifestyle of sleeping with one boy after another comes to an end. It happens when she meets the child Shio, for whom she is convinced she feels true love for the first time. Satou may seem sweet and innocent, but there is nothing she won't do to protect their life together, including committing murder. But from where did she acquire the little girl, and how long can their "Happy Sugar Life" together last?

Included one-shot:
Volume 2: White Sugar Garden, Black Salt Cage (pilot)

Short story:
A short story was released in Young Gangan 23/24 of 2016 which is referred to below as 19.5. It was later released in Volume 6 as an extra.

From Webtoon Live and Shiro Nabi: "Welcome to Survival, 'I Am Unhappy,' the exciting game show to find the world's unhappiest person! The grand prize... is a wish granted by God!" When the victor of the game show wishes for the end of the world, God accepts this wish with a set condition: the world's end would proceed over the course of 100 days, and during that time, he is allowed to 'change his mind' only once. Oh Duk Hee, a quirky comic artist who specializes in unhappiness, is chosen by God to to make the unhappiest person on Earth happy again. With the pressure of mankind's destruction riding on her shoulders, will she be able to change his mind before it's too late? The competition to choose the world's unhappiest human?! The hybrid school fantasy action story by Jung Pil Won!

From Anime News Network:

The first Legal Drug series went on hiatus in 2003. Drug & Drop will again follow the lead characters Kazahaya Kudou and Rikuou Himura. The new manga will reveal Kazahaya and Rikuou's pasts as well as the background of Green Drug, the mysterious drugstore where they work.

Count D has opened his petshop again, this time in Tokyo's Shinjuku!

For those who haven't read Petshop of Horrors, Count D's Petshop is a place where one can find animals from the most ordinary housepets to savage predators to mystical beasts that should belong only in legends. Customers often find that their new pets change their lives more than they expect, fulfilling their dreams, or realizing their nightmares.

Seven college students are coming back from their graduations. During the travel they are shocked to see a strange, cow-like creature with a human face. This accident means they only have seven days left to live. What will they do to stay alive until the fated day?

From Tokyopop:
CLAMP School Detectives focuses on the exploits of Akira, Nokoru, and Suoh - 3 pre-teen sleuths - and their quest to make the CLAMP world safe for the girls in their class...

For an unknown reason, 13-year-old Aki Kasuga seems to have killed her parents when she was found by her younger sister and detective Toru Takahira at the crime scene of lake Ezu near the Kumamoto city. As a minor, the girl joins a reintegration program and changed her name; from now on living as Sei Kamihara.

Six years later, a new crime takes place in Ezu, and this time it's a little girl who dies. A week later, several species in the zoo are found dead. What is the common thread of all these mysteries in Kumamoto?

From Batoto:
Ming Lan was adopted into a new family, but her foster mother Nan Xi treated her as a replacement for her dead daughter. However, her two new brothers, Ming Qing and Ming Jing did not welcome her. Ming Lan's quiet life under this new roof was disturbed by pranks and false smiles….

While humans toil at their ordinary, boring lives, a battle secretly begins among a new species that evolved from humans. They disguise themselves as human children, and instead of maturing into adults, they are each gifted with a different "special power". They are the new humans, known as "Kodomo." Hinagata Heiji is a Kodomo who can bring any inanimate object to life by dripping his blood on it. In order to find his own feeding ground, he keeps transferring to new elementary schools.

Yosora Fujimitsu is accepted into North Gate National Military Academy, a school for the children of the country's elite. Endowed though he may be with the good looks and intelligence the school values above all else, Yosora immediately feels uneasy and out-of-place.

He becomes determined to expose the Academy's secrets, and is thus pulled into its vortex of violence and deceit fuelled by the desire to preserve tradition at any cost.

Satoru earned a name as a genius boy detective, and the police rely on his reasoning skills. His secret, though, is that he is able to see the ghosts of the dead, and they provide him with the hints that lead him to solving cases.

Now that he's a teenager, he has attracted a strange 'ghost' named Kako, who claims that she is actually a god. She goads him into taking more mysterious cases, in the search for a vengeful spirit that wants to kill humans.

Now they are a team... where he solves the cases and she purifies the vengeful spirits!

E Rae, who gathers wicked desires from snakes for revenge. For her, Suk Wol tries to find humans who are cursed by snakes. One day he goes down to the village to search for snakes like any other day, but then hears of a rumour about Lee Jin Sa so he disguises himself as a doctor to enter that man's house. And in there, he finds evidence of a snake with a different aura...

Poverty-strikened Yang Jinghua had an accident. The moment he woke up, he seemed to be 10 years younger. Yang Jinghua thought he had been reborn, and when he was about to step out on the path for a new beginning, Duanmu Xi, appeared before him. He not only told Yang Jinghua that he was dead, he even asked for him to join him.. in a Soul Contract.

From Naver:

Iremy, Enz follows Ethermask around the world looking for a lost magic. Along the way, they find friends, defeat enemies, and uncloak the mystery behind Ethermask's immortality.

It centers on a girl named Wakaba Himekawa, who is aware that she is growing up slower than other people, but otherwise lives a peaceful life. On the same day that she finally gets her first period, her childhood friend Takaya confesses that he loves her. While Wakaba had never felt that way for her friend before, she is still happy, if confused. As she is about to answer Takaya's confession, an alarm suddenly sounds, and a broadcast begins that will change her everyday life.

Denzel Westwood is a young, talented magician without a care in the world, until one day his eyes suddenly begin to turn amber, prompting a series of events which will lead him to discover the truth of the world in which he lives and the mysterious Abyss which surrounds it. This is the story of a boy filled with light.

English version
Original webtoon

From Shoujo Manga Maniac:
Katsuyuki, a gifted, petty and egocentric high schooler, intends to work in the high financial world. His well regulated life explodes when his mother remarries his worst nightmare: a traveller writer, unproductive, nice and completely unpredictable and father of a son who looks like him. All his opposite. Consequently begins the subtle contamination of his entourage by their terrible joie de vivre. Even Nagasawa "the female brain of the high school", the only one for which he had respect for decided to find anew his peace. Katsuyuki feverishly seeks a way for returning these aliens on their planet and he's not sparing with spite.