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.

Even in this day and age, Ninjas walk among us, hide within plain sight, still waiting for their mission orders. However, for some, it takes much longer to receive orders than others! Meet Kumogakure Kurō, a NEET and a Ninja. After being a long time without work, he finally receives orders from the higher ups!

Girl moves into an "apartment" (seems more like a house with a bedroom being rented out) and finds out the landlady is a lesbian. Being the bubbly cheerful girl she is, it doesn't really bother her, but what will happen when the landlady develops feelings for her and starts coming on to her?

From Easy Going Scans:

Lord Perdien is a 1st class demon who has been living in the human world with his son. He has no intentions for his son, Miryu, to follow the path of the demons and while their lives were peaceful up until now, a succubus arrival and a sudden illness of his son are more than enough to disturb their peaceful way of living. He has to make an important choice: Either to let his son die or listen to whatever the succubus offers him for a cure.

This is a story about the struggle for peace and the search for something precious that has been lost for over a thousand years. Six young people, with the help of the ancient weapons that chose them, must work together to solve a millennial mystery before they too become lost.

A 47 page one-shot about how Harold (mangaka of Beck) got to meet the 'Red Hot Chili Peppers.'

An ever changing (and unusual) love triangle story, set in modern Japan.

[From Lililicious]:
Uchida is in love with Nakano, but feels like she can't tell him because she turned him down when he confessed his feelings to her years ago. One day, she sees him with another girl-- Kobayashi. The three begin spending time together, Uchida wondering all the while if Kobayashi is in love with Nakano and vice versa. It isn't until much later that she finds out the true object of Kobayashi's affections...

A story about a mysterious girl who doesn't seem to age and the people she affects. Very earth-friendly.

The daughter of a duke, the stuttering Maximilian, married a knight of lowly status at her father’s coercion.

After their first night, her husband departed for an expedition without another word.

He comes back three years later, this time as a famous knight in the whole continent.

How would Maximilian face him on his return?

"The more I think of you, the more lonely and lonely I become. I don't know why I can't quit even though it's so painful."

Follow the daily hilarious shenanigans of the adorable cats: Huang, Hua, Blanche and Klein.

Under the Rose contains two stories:

Winter's Tale (Fuyu no Monogatari):
In the late 19th century England, Grace King was the daughter of a declined Marquis and also the mistress of Count Arthur Roland. After her mysterious death, her sons Linus and Lawrence were taken under custody of their father Earl Roland, who has a sick wife Anna and other children. Linus deeply suspects that the Roland family was involved in the death of his mother and thus begins his lonely investigation.

Spring's Paean (Haru no Sanka):
Rachel Brennan was hired by the Roland family as the governess for the children. The children, except the second son William, gradually began to like her. Will William also open up to Rachel too with her efforts?

[From Lililicious]:

Under the Rose is a love story between two sisters who meet years after their birth.

From Liquid Passion: 2 color page side story for the famous poetic short story "Under the cherry trees" written by Motojirou Kajii in the early 1900s.

This contains two short stories, one about Bun and a new kid he's found to replace Satoru from Heat; the second is a look at Bun and Daisuke

Miyamoto Kano's "Walker" universe timeline:
1) Are You Enemy?
2) Not/Love
-- Not/Love dj - The Reason Why We Live Together
-- Not/Love dj - Dog Days
-- Not/Love dj - Demonic Conversations
-- Not/Love dj - Brand New Lover
3) Heat (MIYAMOTO Kano)
-- Under the Skin
-- Lizards, Angels, and Daemons

The ones on ( -- ) are doujinshis. They give background or "add into" to some key points in the main story line. So you're not really missing anything even if you don't read it.

Nonomura Heita, a high-schooler, takes care of the last boarder left at his grandfather's house after his grandmother passed away. The boarder is a translator named Miharu, who insists that Heita make a bentou for him every day. Should such a wifely duty be given to a high school boy? Or will the duties someday go beyond just making bentou?

A huge mysterious explosion that occurred in the middle of a city. In(燐), who received a curse from his master and started doing acts of kindness in the earthly world. RyuJin(劉進), a swordsman who is out to obtain revenge for his village. And the mysterious herb merchan Ami(俄靡). Their adventure to find out the cause and explanation for the grand explosion. Original webcomic: http://comic.naver.com/webtoon/list.nhn?titleId=497180

Policeman Brandt has a new mission: to catch the leader of an uprising illegal porn company. But in order to go undercover, Brant has no choice but to do an audition, naked?! And winds up being filmed in porn videos...?! by Snow Flower Scans

The manga begins as Kanae Sekiguchi, proprietor of the Tsuki no Yu bathhouse, struggles to reopen her business after the unexplained disappearance of her husband...