From MangaHelpers:

On his seventeenth birthday, Amamiya Kota was going to ask his classmate Misora Hiyori out. Tragically, he dies in a car accident but is given a second chance back in the living world on borrowed time. He gets entered into a competition called the 13 Game where other people like Kota who were supposed to die return back to the world and given an option: locate and kill 13 other players or suffer the fate of death. Each player is assigned to a handler, mysterious beings with special powers, who use them as if they were characters in a video game. Kota’s handler, Merume, explains that there are players like him all over the country, each with a unique ability that helps them kill, and Kota has to kill 13 players within 1 year. With his demon hands ability that was inspired from his hobby of magic tricks, Kota must unwillingly participate in this cruel game if he wants to live. [vyc]

Satsuki Kakeru lost his sister by suicide and has been living a dull life ever since then. One day, he is transported into a bizarre world "Red Night" along with his friend Minase Yuka and six other classmates. In order to survive and escape from Red Night, they must defeat six black knights in order to return home.

In this small town, within the 49 days after a person dies, you can see the dead's spirit. She once admired this small town where you can still spent time with the ones precious to you within these 49 days, but...

Includes two oneshots (not yet scanlated):
Soko ni Koi Ari (そこに恋あり)
Kimi wa Nanimo Hoshigarazu (君は何もほしがらず)

From ShoujoMagic:
1. 38°C
Taiji's normal body temperature is 38 degrees Celsius, or so he says, but Shiina thinks he's full of it. Taiji is a friend with whom Shiina can always--and does always--fight... Until Taiji unexpectedly confesses his love! Shiina begins to run a fever, but is that the only reason she's getting so hot...?

2. Solution Maze

3. Heaven in Jail

4. Winter's Aquarius

Collection of short stories:

• 37℃ Kissu
Naoki was a very cool and good looking guy, but somehow after meeting Fumika-chan, he's not cool at all, but very cute?!

• Himitsu no Namida (Secret Tears)
He saved his second button for her, but on their last day, she handed him a love letter to give to his best friend. Instead of delivering that letter, he kept it himself, and asked her to go out with him instead...?

• Caramel Kiss
Atsushi-sensei is Kawahara's first love, will he be able to accept her affections?

• Shounen Knife
Until Riki moved in, the house next door to Mimi's was always vacant. Riki saved Mimi's cat, but it seems that he isn't as well mannered as she first thought?

• Extra from Kiss, Zekkou, Kiss Bokura no Baai.

1-3) 37°C no Boyfriend
Wakaba got locked up in an elevator with a completely strange guy. Moreover, they happened to share a kiss. He's someone she'd never meet again... or so Wakaba thought, but it turned out that that guy, Chitose, is the boyfriend of Nao, her friend!
Nao introduced a surprised Wakaba to her upperclassman in her club, Takaomi, but no matter what, Wakaba can't forget about Chitose...
- Awakened Memories

4) Tsukiakari no Himitsu

5) Haru ni Naru Made Matte
(Also included in Houkago, Kimi to Koi o Shite.)

From Noctis Op.92:
What exactly is the difference between a robot and a human?

In a dystopian future in which robots are becoming increasingly commonplace, a young boy named Hogu lives in near poverty with his grandmother and sister. Though he innately possesses a kind soul, he is ostracized by his classmates and frequently bullied. At the beginning of the story, we find Hogu, friendless and alone - until he meets a robot girl...and our story begins.

From Lililicious:

In "24, 25," the main character reminisces about a girl she knew in high school.

1-2) Can't Kiss for 24 Hours
A math teacher who has an intense relationship with the problem student, Kikusui Kiyoya. Even though they were a couple in love, one day, Sensei suddenly wants to break up...?

3) If I Didn't Have You
Fujisawa Yuu just moved to a new town. On the first day of school he's warned to stay away from Nanatsuki Haruki. The word around school is that Nanatsuki who is actually 20 years old will sleep with anyone, but only at school. The mystery is why he only sleeps with people at school and why hasn't he graduated yet?

N/A

Ikumi and Kunitachi are finally hitting it off steadily. However, trouble starts once again during Valentine's Day when Ikumi received a box of chocolates containing glass and became the victim several other pranks. In the end, when the person revealed himself to Ikumi, the past was unfolded.

Unconsciously jealous over what he's afraid to know, Ikumi threw a fit and said something cruel towards Kunitachi. Unable to take it, Kunitachi raped Ikumi...

From Chibi Manga:

5 years ago, Shin was Yumika's private tutor. Now this Shin-kun comes to Yumika's high school as a teacher trainee! But their love from 5 years ago will most probably start to bloom again?!

From Midnight Scans:

Yumika’s first love was her tutor Shin. As she hope to meet Shin once again, which really happens, how will Yumika proceed on to confess to Shin about her feelings…

1) Water Breath
An injury destroyed Olympic hopeful Ryuji Hayashida's promising swimming career. He was transferred to a university where he believed no one knew who he was, but he was wrong. There was someone who recognized him the moment their gazes met at the university's swimming club.

2) Pension
A tempestuous tale of a rock band and the consequences of their enigmatic guitarist's return. It didn't take long to realize he has a keen interest in their lead singer.

3) Dance
Shachi never got over his feelings for his classmate Michio who jokingly danced with him at school. Years after their school graduation he discovered what Michio did for a living. The discovery inspired him to sell his father's car for one night with Michio, which turned into a different kind of dance.

4) Longing
Shy and timid high school student Sakaki has always watched his classmate Ryoji from afar, but he wasn't as invisible as he believed himself to be.

The student council president is gaga over the vice president, but her feelings may or may not be returned. In the meantime, it's up to the serious and by-the-book vice president to keep the flaky (but surprisingly effective) president on track.

After she died from an accident, Ria become angel No. 5623. She could not forget her life from when she lived. She misses Ban Ji Hwan, her boyfriend on Earth, day and night.
1 year later, Ria happened to see Ji Hwan's name on the death list, the list of every names who is about to die in 100 days. Ria begged high-ranked angels to let her save Ji Hwan. Ria entered the body of So Hae, a shy girl who is tired of her life, the opposite of Ria's personality. Enduring the bullies from step-siblings of So Hae, Ria did her best to bear everything in order to look for Ji Hwan. But when she found him, Ji Hwan cannot recognize Ria...

Two girls start their freshmen year of high school. However, the two girls after years of being together are separated. One of the two does not take this easily and her world falls apart.

This is a cinderella-like story in which a shy and common girl gets a pair of glass slippers. The slippers enable her to transform into a cinderella. In this form she's loved by the guy she has a secret crush on.

From Shoujo Crusade:

One day, while in search for more food, our heroine stumbles upon a jar of what looked like umeboshi; little did she know that it would bring her more than just a full stomach. The mysterious snack somehow makes her shrink and she can only grow back when she eats something (which is a bit of a chore if you're THAT tiny). And if that's not troublesome enough, she's also dealing with her crush who seems to like her best friend!?

From Yes_Rhade:

Chuunri's in a predictament - he's newest boyfriend doesn't seem to be interested in being intimate, so he goes to his previous boyfriend for advice. Of course, a little jealousy never hurts to get some action going.