From Blissful Sin:

"Please marry me, Asakusa." Though, I thought I was asking where Asakusa was. Alex, a traveler from England, wanted to get to his destination, Asakusa, but he got lost in a quiet residential area. He unleashed the only Japanese words he knew at a man walking towards him, incorrect Japanese taught to him by a friend who was playing a prank! But the other person blushed and replied, "Yes"...?

From Blissful Sin:

A sex battle between the selfish young master and the wild detective!

After a certain incident, an excellent policeman named Jin loses his job. No longer employed, he decides to become a private investigator. One day, Kujou Anri, the young master of the Kujou family, walks into his office pretending to be a client. Instead, he ends up confining Jin! What was he really after when he bound and drugged the detective?

These adult oneshots have finally been gathered into one volume! There will be plenty of man-boobs and extra drawing to spare!

Everything has been a contest between Shou and Tatsuo since they were children. Now they've admitted their mutual attraction, a new competition begins... Who will top?!

Source: Blissful Sin

Yaneda Shigeru is a guy living alone with his cat, Konbu, until she turns mostly into a human (she keeps her cat tail and ears) for unknown reasons. Though to Shigeru, this isn't a problem; he has a cat-girl fetish. The problem is, Konbu is stuck-up and wants everything to be elegant to fit her high-class tastes, even her name to be something more high-class. So, they each want to mold each other to their tastes; Shigeru an elegant butler, and Konbu an obedient, cute cat-girl. Will one of them win, or will they come to some sort of mutual understanding?

1-5) Stay Gold
After a failed attempted at bleaching his hair and ending up in a fight on the day of the entrance ceremony at his high-school; Ken is already off to a bad start with a bad first impression as nothing more than another delinquent.
Mizuki, Ken's best friend and secret crush, was the only person he met after that not to label him negatively just because of his appearance, but maybe that's because neither is Mizuki just the cute and innocent guy he appears to be.

6) Kamu (I'll Bite)
Warning: non-con/rape
They've been childhood friends since they were nine, but ten years worth of feelings suddenly break out and one of them crosses the line.

7) Slave of Love
Warning: non-con/rape
Riku just wants to find love... but every time he gets a girlfriend, he's quickly dumped - one time within 10 hours! The only one who will listen to his love problems is Arata, his super popular best friend... but could Arata have something to do with his love problems?!

8) Ultramarine Sinbad
Tomohiro and Shigeru are happily dating with lots of hot smex.... the only problem is, Tomo doesn't know if Shigeru loves him or surfing more. He tolerates Shigeru's selfishness, telling himself to be mature until one day Shigeru pushes it too far and he snaps.

8.5) Soldier of Love
Short story about 27-year-old Ichiro and his boyfriend Haruya who's 10 years younger.

Tatsuhiro moved to Tokyo to attend an art school and start his new life. In his new room, there’s a small hole in the wall. At first he can see nothing through the small hole, but one night, through the peeping hole, he saw a girl. That’s how his new life starts.

Without doing much research on the school or surrounding areas, Hibino Ryouichiro picks an art school in Hokkaido. Tricked by the school advertisements, he goes to the campus only to find out it is a desolate and cold campus. The only glimmer of happiness for Ryouichiro are the girls on campus. Just hours after meeting Kisaragi Riho, the cute girl on campus, she seduces him only to find himself outside naked after she is done with him. Feeling heartbroken and used, he finds comfort in Aso Tomoe, who lives on the floor below at the dorms. Although it is freezing outside, it is hot underneath the sheets for Ryouichiro.

From Shoujo Crusade:

1-3) Lovers in Conflict
Because of her sister who suddenly ran away, Sagiri ends up getting married in her place. Her husband is hard to understand and is a bit of an S. What will happen to their married life?!

4) Wild Rose's Crown

A series of interconnected romantic comedy one-shots involving a Royal Family with 7+ sons in line for the throne and the men they fall in love with. The series also occasionally chronicles the romances of other palace employees and secondary characters. 1) Prince vs Slave - The youngest (7th) prince Shuki, gets hugged by new slave, Fuanron, that seems to know young prince. Shuki starts to bully the slave till their roles get reversed and he even takes place of the prince's teacher, Riiren. Who is Fuanron in reality? 2) Prince vs Assassin - 1st prince, Ryuuen, gets attacked by Seiran, but he defeats him and makes a deal: the assassin can try to kill him all the time, but if he fails, then he must spend the night in the prince's embrace; and so starts Seiran's life as an official consort. 3) Right-handed Priest vs Left-handed Priest - Rei has been in love with Ryuuen (the 1st prince) for years and now he has finally become the minister of the right. He thinks he can get closer to the 1st prince, but there is an obstacle, the minster of the left, Rai, that says that he is in love with Ryuuen too. 4) Mercenary vs Prince (vs The 4th Gun-Warrior?!) - 6th prince, Kagetsu, fell in love in Jin, who helped him with his wounded feet. Now he escapes from the castle everyday to tell Jin that he loves him, but the mercenary doesn't believe him. Suzaku always comes to drag Kagetsu back to the castle, but what are his real motives? 5) Scramble Showdown (?) - Short comics (one page for each) with pairing: Jin x Ryuuen x Seiran, Rai x Seiran, Kagetsu x Fuanron x Shuki, Rei x Shuki (x Rai x Fuanron), Suzaku x Riiren x Tailor. This story of 2nd prince is also featured in the manga, Ousama Game. 王子様★ゲーム

From Fantasyshrine:

The Instructor Demands ABSOLUTE obedience!!
A forceful love between an army officer and his student!?

During WWII in Japan, Yamato came to the Imperial Army Academy with the dream of becoming an officer! However, during his entrance exam, an elite instructor named Onizuka pushed him down—!!

The super scandalous love between an egotistic instructor and a prideful top student on campus!!

Fujisaki is madly in love with his boss, Minemura. But Minemura is starting to get bored with their sex life and suggests seeing other people. Can Fujisaki convince him it's better when there's love?

A girl and her boyfriend of one month plan to go on an overnight trip to a spring, and she expects that "it" will happen, but...

Collection of oneshots

From Blissful Sin:
With naked bodies in close contact at a hot springs inn on a school field trip, they’re hot to trot! ♥ Horny Keitatsu’s erotic rampage on Ran just won’t end!
The boys from “Bousou Kareshi” – Keitatsu x Ran, Seisuke x Tsubaki, and Himura the shota-con public health doctor – all are getting worked up and having extremely perverted sex! ♥
The climactic comic!

1) Punishment Sweets
Misaki forgets his boyfriend Rui's birthday, how can he make it up to him?

2) Love Fever Boy

3) Hot-to-Trot♥Boyfriend

4) Phantom♥Boyfriend?!

5) Love♥Fighter!

6) Oppai Fighter!

7) Himura-sensei no Junan (The Suffering of Dr. Himura)
Himura Yuu is a high-school doctor with a serious shota complex and there's only one person standing in the way of his virtual smorgasbord; his colleague, Ashiya. Himura is clueless as to why Ashiya interrupts him everyday, but when he learns of their previous connection, things become all too clear.

8) Himura-sensei no Moekare (Himura-sensei's Moe Boyfriend)

9) Lonely Little Bird

10) Love♥Love Je t'aime

Collection of oneshots. Very steamy!

1) When violated by the perverted school doctor, Mizuru calls out the name of his best friend Natsura. But it's his best friend, he can't possibly be in love with him...right?! With Natsura being mute and Mizuru not being true to his real feelings, will these best friends have a happy (and smex-filled) ending?

2) Ibuki has known that he is different from other boys since he was 12, but he has been able to keep it a secret. However, his dad's new Italian apprentice (who wants to bathe together!) is about to shatter Ibuki's resolve!

3) Hachiya always felt Hozumi's eyes on him in high school, but never talked to him. Now they meet 8 years later in a gay pub but is it just coincidence? Or destiny?

4) Takashina has an imaginary friend name Michael...an imaginary sex friend that is! But he wishes to fall in love with a real man. Maybe his friend Toriumi could be of assistance?

5) Okabe is an artist who doesn't go out much. The first man he fell in love with is getting married soon, what is this difficult feeling? In comes Akiyo, a gay janitor who touched one of Okabe's sculptures. Can this straightforward and simple man show Okabe the world outside of his easel that he's been longing to see?

6) Our Sin

7) Lovesick Baby

From Fantasyshrine:

1-2) Keigo and Gunji are both stubborn and prideful men who didn't realize their mutual love for each other until years later when both ended up in the same hot spring together... with their kids!? Will they come to terms with their feelings for each other?

3) Sweet Honey Drops
Gunkichi and Keita (the kids) are growing up and falling in love.

4) Act.
For Ryouchi it's love at first sight with actor Sou Seiji. Getting a job near his idol is the first step for Ryouchi, but of course, Seiji is not the person Ryouchi thinks he is.

5) Dandy at Dawn
Newspaper writer Tetsuya manages to implode his big city life and has to move back to the country. Waiting for him is neighborhood boy Kyosuke who's gotten much bigger in his absence.

From Peccatore Sanctuary:

Because of a painful past memory, Kanan can't believe in love again. Yet after meeting with the priest, Jake, he begins to experience the joy he longs for. Even the strong posessiveness of Jake's, that is beyond normal, to Kanan is also a wonderful feeling...!?

High schoolers Yuki and Shigeru aren't dating, but still enjoy a highly active sexual relationship. Naïve and still very child-like in the way they think, it comes as a great shock to them when Shigeru discovers she's pregnant. The two are confronted with the decision of aborting the baby and wounding Shigeru, or to keep it and face great opposition from their parents and high school, and *gasp* miss their beloved Conflict concerts!

Amamiya just died. Death by bottle tripping... But he is given one more chance, to live... To live in the body of a girl gone comatose, that is. With his new identity, read on how his mind set is slowly changed from a guy to a girl. One thing's for sure, there is more than one body switching in this manga!

From HotCakes:

The man super-uptight office worker Ooizumi Sonoko got drunk and spent the night with shows up at her work and turns out to be the section chief?! A hilarious romantic comedy about pure love wrapped in indecency.

This series was published as part of vol 2 - 5 in Oboretai and the first 3 chapters(done by ShoujoMagic) can be found in vol 2.

Haruru Shirosaki, a girl whose father is a director, is always busy. Her best friend is Mami. She visits a girl's school across the road from a boy's school. One day she sees a boy in the window of the boy's school. When she comes home from school the boy she had seen earlier is there saying he will become her butler? Is this just a dream?