From Viz:
It is the middle of the 21st century and Tokyo is expanding more and more, filling Tokyo Bay with landfill to make room for the bursting population. But suddenly Tokyo suffers one of its greatest earthquakes, and the landfill liquefies, creating untold damage in the newly-made urban area. The members of Self-Defense Force Rescue Squad Four are sent to help. But what they dig up is a plot of murder and destruction--one that wipes out nearly the entire squad and leaves its two surviving members, the fierce Rei and her cool, handsome partner Uozumi, in a fight for their lives.

There is only one place where they can find the work that keeps them alive, and the support so they can start uncovering the mystery that killed their squad: that's in the south-Shinjuku bar called Chicago. As the earthquake levels Japan's largest city and capital and leaves countless dead, rescue workers, Rei and Uozumi, search for survivors amidst the rubble of Bay District D only to find a mysterious string of dead bodies--bodies with bullet holes. Without warning, the pair is under fire from the air as a hail of gunfire rains down. Are these the killers, and if so, what is their purpose? Barely escaping with their lives, Rei and Uozumi discover that their squad is listed only as "collateral damage" and their records wiped clean.

"Do you know who I am?" Rebecca, a girl with no memory and a missing shoe, arrives at Angus's private detective agency. She found his business card in her coat pocket, but Angus does not know who she is. Angus invites the shivering and frightened girl into his warm home where he lives with his young daughter. Soon they become powerfully attracted to each other, but on the morning after they first make love, a man claiming to be Rebecca's fiance appears...!

From Tokyopop:

Fujiwara Sunao is a rather unusual young lady. Not only does she prefer to wear her hair short and dress like a boy, but she also possesses the power to control water! One might think Fujiwara would be an odd fit at her school, but strangely, she's not. Between the destructive and demented school president, the kooky and somewhat stalker-like school nurse, and the obsessed underclassman who wants to be her apprentice, Fujiwara may be the sanest person at the school--which is a big help considering she may be asked to save it!

Biblia Koshodou no Jiken Techou is a mystery series in which Shinokawa Shioriko, a young owner of a bookstore in Kamakura, unravels the mysteries of the ancient books that are taken there.

The story begins with a young man named Daisuke, who practically grew up without reading books due to his phobia, who brings the complete (and autographed) collection of works by Natsume Soseki, (Japanese writer of the Meiji era) that he inherited from his grandmother, to the mysterious bookstore. Will the shy and introverted Shioriko solve the mystery of the books?

Kisaragi Akira is a police officer investigating a murder case that reminds him of his past.
The memory that he forced himself to forget.
And the past that he buried in the deepest part of his heart.
The clock that was once stopped has started ticking again.

From Titania:

A manga about people trying to kill themselves, but weird stuff happens instead.

01 - Group Suicide
02 - Strange Tale of the Pylorus
03 - Paradoxical Night
04 - Dr. Suka's Villa
05 - The Spirit World Project
06 - To The Dazzling Future
07 - The Licking Woman + Mystery Pavillion (Ones-shots)

A mystery/action plot: in the 13 hours 13 children spent in space, what had happened?? It starts off 8 years after the spaceship incident, centered around one of the 13 children named Bono U. Meyer. He has an IQ of 240 and it seems people who are close to him have [coincidentally, perhaps?] been driven clinically insane. What is going on?

Iori and Nachi are the "perfect pair" of the bodyguard agency Shelter. Partners since childhood, they bicker constantly, but when the latest mission threatens to separate them, is that really okay...?

From Mangascreener:

The only common feature running through these stories is a grown-up protagonist somehow coming face-to-face with his childhood past, in a testament to the loss of youth, the disillusionment of growing old, and nostalgia for better times.

In the Adachi pantheon, this is a rare diametric view of his eternal theme of "youth," in this case youth as seen through the lens of the past. It's a powerful statement from Adachi that might even be an acknowledgment of his steadily-creeping age.

What is impressive about these stories is not the plots or characters themselves, but the absolutely perfect way he tells them, another facet of experience that comes with age. Most of the stories may require multiple readings to fully appreciate the airtightness of the plot and visual motifs."

Susannah is an editor. During a party at a book fair, she sees a portrait of a woman who is wearing the same red necklace as her. Intrigued, Susannah steps closer to the painting, only to be engulfed by a mysterious light that transports her 100 years back in time! To make matters worse, Kane Wilder, CEO of an IT company, who is convinced Susannah is his brother's mistress, accidentally travels with her!

English publication via Renta!

This is an original story expanded from the STEINS;GATE game, and focusing on the heroine Amane Suzuha. In 2036, a monopoly on time machines has created world peace, but at the cost of human liberty.

Suzuha has followed in her late father's footsteps in fighting alongside the Valkyrie rebellion force to change the world. After the group fails on a major mission, Suzuha has almost no hope left. But then she discovers that her father left something for her: a time machine. Using this, maybe Suzuha will have the power to finally destroy this dystopian society and create a better present and future!

Toshiki is a below average student and often the target of ridicule. After he accidentally runs into a shop sign and breaks it, he enters the shop and finds out it will sell him abilities.. But these abilities don't come cheap.

Alternative world where Japanese culture kept its ground to this day and further. Protagonist, a female entertainer typical to Japanese traditional customs, finds herself swept into the world oh so familiar, and yet so different from the one she lived in so far.... a world where she has to fight to survive.

Shishigami Takashi has, for a long time, met with murder cases wherever he goes, that’s how he got the nickname; the "Shinigami" detective. 、 Shishigami, his wife Michiru, and his kouhai Seki, take a trip to an onsen. However, as soon as they arrive, a corpse is discovered...?! Aside from the titular story, two more mysteries are collected into 1 volume!!

There is a rumor going around about a CD called “Trigger” that can supposedly increase the intelligence of its listener. However, the CD has also been connected to several deaths and disappearances. Chitose’s best friend Hayato has also listened to that CD, and not long after, Hayato and his whole family suddenly disappears. Refusing to believe that Hayato is gone forever, Chitose becomes determined to find his best friend and reveal the truth behind the CD.

From: The Zero Alliance

Petey is a bounty hunter in a time and place full of bounty hunters. The criminals are outnumbered by the bounty hunters and whenever a wanted poster is posted, it doesn't stay up for long. Except for one... there's one wanted posted with a negative bounty and no one wants to catch this criminal. But Petey is curious and she seeks the help of a mystery solver...

From Aerandria Scans:

Kanade has an exceptionally acute sense of smell which allows him to detect even the faintest aromas in the air around him. Together with his French cousin Anais, he follows those scents all the way to the heart of the deepest and darkest mysteries.

From Storm in Heaven:

Judges are the messengers of the Central Government, sent out to punish delinquent cities. They have the ability to control programmed "seeds", causing explosive growth. After a disease breaks out among the "Children of Babel", those Judges who're given power through Central's research, Central requires the data of a natural Judge like Sion. However, Central is also interested in the legend of the "Heavenly City", which Sion is named after; what could their true purpose be?

Etou Kai may look like a squeaky-clean kid, but the Greater Kanto Narcotics Control Division's new investigator hides a violent alter ego and a dangerous past.

With his stoic partner Kurabayashi Hal, Kai is assigned to track down and stop the distribution of Dragon Speed, a dangerous new drug. But Ryuugen, the syndicate trafficking the drug, is almost impossible to infiltrate. Add street violence and a jurisdiction war with the Meguro Police into the mix, and it looks like Kai's in for some very long days at the office.

　Our protagonist, Inoue Konoha is still being led around by his senpai, the Literature Club's President, self-acclaimed "Literature Girl" who loves stories so much that she can eat them, Amano Touko.

　One day, someone put in the Literature Club's "Love Consultation Post Box" a bunch of paper scraps that have the words like "Hate", "Ghost is" and a bunch of puzzling numbers on them. Calling the act as "picking a fight with the Literature Club", Touko once again got Konoha involved in her investigation; but when they found the culprit, this girl turned toward them, smile, then said "I'm already dead."

　This is the second arc of the popular bitter & sweet school mystery series.