In the Under Grand Hotel (2013) series:

V.1 - Kiss & Kill
30 meters underground, a prison where escape is impossible; the United States penitentiary, The Underground Hotel. Only the people who enjoy living in this place, a life cut off from the sun, call it by another name: The Under Grand Hotel. Absorbed in pleasure-seeking sex, the shut-call, Erie (leader of the prisoners) isn't watching the men he's raping each night, but rather one man alone. Norman.

Norman, who keeps trying to harm himself as a result of trauma, the kind doctor who cares for him, Van, and Erie, who's falling into a brutal love that's more akin to hatred. What will happen when these various feelings are made to intertwine into a closed-off world? From storyteller Sadahiro Mika, the long-awaited, mature love story of the Under Grand Hotel begins!

V.2 - Last Dinner
Erie is send to level 4 of UGH and reunites with an old acquaintance.

From Blue Flor:

A series of one shots about couples' struggles and happiness. The subtlety and tensions of the stories are all aided by Shigisawa's delicately realistic style.

1) Cool and sweet
2) Happiness or Unhappiness
3) A woman with glasses' agonizing pain
4) Cheap Sweets
5) Meeting up at the end of the world
6) The person to keep
7) A secret word
8) Let's meet when it's time to give up
9) Storm Hill
10) If only you never existed
11) 8PM: offense and defense
12) A little bit bothered

From Blue Flor:
Life is hard enough as it is without the complications love interests bring. However, it becomes even more complicated when the interest in question is a friend. How does one choose between what is right and what is wrong? The male friend you've always been with or the one that's recently come back?

This is a set of five short stories about the trials and tribulations of five different women:
1) Diamond
2) Only 5 cm
3) Inside the Mosquito Net
4) Inside the Mosquito Net 2
5) Hide and Seek

Tabi traveled on a train to a town to meet her childhood friend, Kou-chan. When she arrived, she met Officer Nishimura and an energetic young man named Yukita; both of which were surprised that she came on a train that has never come before.

Shortly after arriving, she discovers this town isn't ordinary in the least, and has puzzling problems. Certain roads in the town will try to "eat" people by randomly dropping them into a deep pit. The town resets after each day, making the same events as the previous day occur. The townspeople don't notice anything out of the ordinary, forgetting each time--the only exceptions being Tabi, Yukita, and Nishimura.

From Shoujo Sense:

I've been watching you attentively from close by... because I fell in love with you.
Only once... although we have spoken only this one time.

Enjiro is a talented baseball player, but has to quit due to a 100 million yen debt. Komado's family runs Benten High School, but the school is on the brink on bankruptcy and (for some strange reason) the only way to save it, is to win the National High School Baseball Tournament (a.k.a the Koshien Tournament).
Seeing Enjiro as their savior, Komado offers to pay him 100 million yen, if he joins the school's baseball team and wins the Koshien Tournament.

From Village Idiot: To Minagawa Ichiri, both good things and bad things are bothersome. That's why his principle is to avoid doing anything that would cause such a thing. However, there is one thing that he can't avoid - because of his parents' jobs, he was constantly transferring from school to school. This time, he has transferred to Reimei Academy, one of the five famous private academies called the "Seven Sisters." On his tour of the school with vice president Kirishima Shitone, an attack occurs! The attacker seems to go after people with long black hair and a sword in an attempt to find and exact revenge on "Double Edge," who killed one of her best friends using a power called "Idea," where she brings her principles into reality using a wrist band called "Codec."

From Eternal Bunny Love:

Colors. Death. Life. Questions. More questions. Will they be answered? Maybe a Roman could shed some light...

Based on an album of the same name, by the band Sound Horizon.

Is it a pumpkin? An oddly-shaped couch cushion? No... It's a CAT!!

When 20-something animal lover, local beauty and airhead Satou Moe happens upon a spherical orange tabby cat in a back alley while stumbling home drunk after a party, she doesn't think twice about taking him in. "Poyo" neither looks nor acts like your average feline, but that doesn't stop Moe, her dad and their neighbours (not to mention said neighbours' pets?!) from loving and pampering him anyway.

[From ShoujoMagic]:

This one volume work is a collection of selected stories from Kayono's "Arabian Nights" series.

1) Princess Man & the Magic Lamp -
Princess Sonia has been kidnapped and is being forced into a political marriage. "By no means will I lead such a life!" she proclaims, and then escapes from the castle and has a fateful encounter with Sinbad! At first she thinks she's jumped out of the frying pan and into the fire, because Sinbad seems like the worst man alive, but then they embark on a journey to seek out the "magic lamp"!?

2) Tearful Madonna.
Mink is a beautiful professional killer whose mission is to sneak into the castle of the Vampire Noa Tribe to assassinate their leader Orion.

3) The Beautiful Face Tribe.
Rin pretends to be a rich girl in order to marry a wealthy man and save her father from a 100,000,000 yen debt. However, she must first choose from one of the three brothers... The oldest is a singer for a rock band, the second son is a fantastic chief, and the third is a high-schooler too shy to speak yet wishes to become an actor. All have a tender heart; so, which will she choose... or will she sacrifice her father and her future by telling this family the truth about her intentions.

High-school student Nanamura Hikaru has little memory of his deceased father, a famous playboy actor, until his father's suave attorney, Shimogura, contacts him with the promise of a sizable inheritance. The catch? Hikaru has to make contact with his eight half-brothers - the fruit of his father's philandering ways.

Eighteen-year-old Mutou Kunimitsu sees how political injustice is committed all the time and that the government is profiting from the poor and labor class. So, he decides to change all of Japan. Here starts the legend of the man later known as the "Japanese Don."

Won the Kodansha Manga Award for Shounen in 2003.

Haruka Kotoura is a 15-year-old girl who can read people's minds. She has been suffering from troubles caused by her mind-reading ability, and her parents got divorced as a result. She moves to a new high school but tries to keep away from her classmates. Yoshihisa Manabe, one of her classmates, accepts and appreciates her ability and she begins to interact with her friends with his help.

From Echochi Scans:

Cram-school teacher Kikuchi Hideo woke up one fine morning to a message from his ex-girlfriend telling him that she was seeing someone else. Having to go to work after such a crappy experience, he was faced with his university friend's, Sera’s, boyfriend Akaboshi Tomohisa who was also his adorable student. Usually Akaboshi’s rather stoic and aloof but in front of Sera, he just brimmed with so much happiness. Sadly, Sera harboured a secret that will threaten their relationship and poor Kikuchi, being Sera’s good friend, knew about it is caught in between. It didn’t help that Kikuchi’s falling for his student too…

N/A

Takuma Zushi just wanted to be left alone. He sleeps in class and skips club. While going home, he sees a girl walking into the woods and decides to follow her. There he witnesses a fight between two sword masters with the prize being the ownership of the "Kandachime", a sword that can take human form. That girl, Otowa Hagane was about to lose when he naively steps into the fight...

From DrCoke at MangaHelpers:

When Kamiyama Keito saw Oomiya Honden High School's (a.k.a. "Denkou") Rock Band "Kei-On" club, he was immediately struck by a sense of awe and admiration. Once he was admitted into the school, he immediately joined the club. To the despair of Keito, the club was run by two degenerate senior students who forbid any real practices. Once spring break turns around, Keito finds out that the two seniors were arrested for possession of marijuana, in turn pushing the club into the brink of termination. With the help of the only other member of the club, Tsukumo Shintaro, will Keito be able to prevent the termination of his club?

From Yen Press:

It’s Noh-A’s first day at Amityville High School, and her reception is chilly to say the least. Brutal might be a better description! Decapitated but not dead (or is she??), Noh-A quickly realizes that nothing is as it appears at Amityville High where paranormal creatures battle for supremacy. Caught in the crossfire, Noh-A may have to rely on the unlikely (and possibly unreliable) aid of the most sinister student at Amityville… the deadly Jack Frost!

In the age of Feudal Japan, the land is roaming with zombies and towns after towns are getting consumed by the monstrosity spreading like wildfire. In the midst of this, a girl is looking for her father.