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

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.

A sixteen page seasonal short! Futaba, the loneliest gay student in the world, has a crush on his best friend, Toki. But Toki is straight, and Futaba will never do anything to mess up their friendship...

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?

Kei is interested in a woman at the gym. Imagine her surprise when she sees her in a lesbian bar!

• The Power Plant
• Vacation of the Power Plant
• The Great Traffic War of the Power Plant

• Hidarigawa ni Ki o Tsukero (Guard Your Left)

• Aru Eiyuu no Shi (A Certain Hero's Death)
Imagine, that the roles of whales and humans were swapped. So whales (or whale-like creatures) would be rather small, able to talk and smart. Humans would be large, stupid and hunted by whale-people.

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.

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.

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?

"Lured by the sweet fragrance of the flowers which blanket the earth, with fangs of steel and claws of iron, to the Garden of Eden which welcomed the ages, under the guise of a disaster from the heavens... seven dragons appeared."

Based on the game with the same name.

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.

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.