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.)

About a play-girl goddess from heaven who is stripped of all her 'goddess' powers and reborn as a human. The story progresses as her incarnated character learns to live, love and find what true happiness is all about.

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.

Thief Gintonic seeks the mysterious treasures known as "The Three Hearts". One night a mysterious woman falls from the sky claiming to be an escaped Princess from a sacked castle. As fate would have it, she has one of The Hearts. But is she really who she says she is? And will Gintonic let her live to fulfill her mission?

There’s one thing I understand when I became an adult.There’s nothing special about boyfriends, sex and kisses. but if I think that, will I be able to find love?

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?

From Tokyopop:

Akira - who later appears in the CLAMP School Detectives manga series - is a dapper, debonair young thief-for-hire who becomes the object of 5-year-old Utako's affections.

From Boys On Boys Love:

1-2. 2-dome no Koi no Hajimari wa
After being harshly dumped by his lover, Kousaka Yuuki, a shop manager at a restaurant, swore that he would never love again. One day, he meets his ex again when he unexpectedly shows up at Kousaka's shop. It was then completely exposed to Matsuoka, a kouhai at work, that he dated a guy. Kousaka was shaken that his past was known to Matsuoka, and worried that he would look down upon him, but Matsuoka forcibly kisses him and says "I love you" to Kousaka...!?

3. Gekiai Honey
Sasaki Ryoutarou, a part-timer at a restaurant leading an ordinary life, suddenly met his old classmate, Mio. Mio was once a gloomy guy ignored by all, but is now a cheerful, completely changed guy. He claims to have been searching for Ryoutarou to be his lover because he couldn't forget about him, even after being rejected a long time ago. Mio changed his style because he had heard that Ryoutarou's type is a cheerful person. Ryoutarou refuses to go out with him, to which Mio responds: "go out with me for a month, if you don't fall in love with me then I'll go back"...

4-5. Honey Trap
You is in love with his best friend Shinji. Afraid of ruining his friendship with Shinji, he doesn't confess, and breaks off all contact with him. Three years later, running away from some stalker, he enters a building and asks for help. However, it turns out that the man living there is his ex-friend Shiniji, who is now a detective...

But what will happen when Shinji suddenly asks You to be his lover?

6. Bokura no Koi no Hajimari wa

- Extras
Is a small continuation about the first story.

N/A

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…

From Beautiful Soup:

"1999" is an angsty and widely varied series about a bunch of teenagers. One of them is the son of a drug lord and so as you can imagine, all sorts of shit goes down, surrounded by a backdrop of convoluted and fluctuating interpersonal relationships.

This is a plot heavy manga with some mildly-explicit sexual activity.

MAL:
This plot takes a new twist to Romeo and Juliet's forbidden love. It's July 7th, 1999 in Shanghai and there are two gangs fighting for control. Only in the ceasefire zone do people live in peace. In a chance meeting Xiaoxue, who is part of the Toulon's gang, and Dawu, from the Xianglongji's gang meet by chance and without knowing they are enemies. In the heat of the moment Dawu takes him to a place he has the keys to in hopes Xiaoxue will join him, but is turned down. With a simple kiss he leaves Dawu not knowing they will meet again, but in very different circumstances

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...

An art college students moves in Venice to study, she starts to live in her new room, part of an old huge historical mansion and she discovers a new world of secrets linked to her young, mysterious landlord. A gothic romance story and a vampire tale which flows around Venetian laguna and roman museums; a manga rich of suggestions and images with a passional storytelling, a deep noir drawing style and melancholic mood. From Italians to Japanese. This was created for Kodansha, published on Amie. You read it Japanese style.

Kazao is happy with his life on Mirai ("Future") Island. Sure, his parents abandoned him after he was born, leaving him to be raised at the orphanage-like facility, but his life is comfortable and has his friends, especially the lovely Eiko, the girl he loves. One night, however, he has a horrible nightmare where he sees himself die in a motorcycle accident. After that, everything changes. The next day, his parents are miraculously "found" and he is torn from his idyllic life and Eiko's side to be thrust into a world he knows only from television shows and school assignments. Dropped unceremoniously in the middle of a city with only a sketchy map for guidance, Kazao is saved from wandering aimlessly in search of his new home by the cute and forward Yuu, who turns out to be in his class at his new school as well. Despite his best efforts to accept his parents' sudden return and Yuu's friendly overtures, Kazao can't shake the feeling that things aren't quite right. Nor can he forget Eiko. Why did his parents wait sixteen years to call him back? And why is the piano the only used piece of furniture in his parents' new house? The mysteries begin to pile one atop the other as the lies fall apart in this intriguing story of future possibilities and innocent romance.

From Dark Horse: A vacation fling was completely out of character for old-fashioned Carol, but her attraction to intriguing, older Marius tempted her to break her own rules. The next thing she knew, though, he'd turned up working at her hospital! Does she have what it takes to attract-much less keep the attentions of-this intimidating, sophisticated, and utterly compelling man?

From Manga Updates An ordinary high school girl, Lin Seonu, unknown even to herself is actually a woman saint holding ancient power called the "Jade of Bango." On her seventeenth birthday, she obtained the power to see ghosts, and every morning after that she goes to school accompanied by the harmless and lovely ghosts. One day, however, Lin has an abnormal dream, and that evening, she encounters a terrible evil spirit. Shivering in horror, she is rescued in the nick of time by a handsome man she had seen in a dream. He frees the ridiculous power that had been concealed in her. He says that his name is In Mu, and that he is her fiance.

There is a mysterious group of people who inflict cruel and fatal games on people for their own amusement. Tatsuya and Misa are out on a date in an amusement park when they wander into one of these horrific competitions on the tallest roller coaster on earth. The seats fall out of their 12-person roller coaster car, and they are told that the game will end when all but one person has fallen to their death. Will the passengers be able to find a way to escape the competition? Will there be any retribution against the orchestrators of this sick crime?

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.

7 Short Stories About Sex (spanning across 11 chapters):

1-3. 7 Daime no Tomari (The Seventh Generation, Tomari)
Tomari is a cursed woman who must do specific sexual things with her partner or the curse will kill her. Her partner, randomly chosen by the curse, is a guy called Naoki. He's pretty much willing to do whatever she needs, but Tomari will have to get past his incestuous sister Kyoko first.

4-6. Hajimete to,
A teenage couple, Seriko and her boyfriend Ogihiko, find themselves caught in a plot from her crazy yakuza family to make them lose their virginity together.

7. Sandy Go Home
Yoko returns from studying abroad in America with her sex-crazed roommate Sandy, and they both proceed to fight over who gets to have sex with her brother.

8. Mete Yunde
After their parents died in a traffic accident, Morote's two older sisters became insane. Is he safe in the house with them any longer?

9. Pastel Ivory
School kids have a sexual encounter in a bathroom.

10. Ninjia Shoujo Makari Tooru
When a ninja invades a girl's bedroom, he finds himself completely outmatched by her skills, both ninja and erotic.

11. 80D
A couple has a sexual exploit in a library after hours.