From Lililicious:

In "24, 25," the main character reminisces about a girl she knew in high school.

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?

N/A

Ikumi and Kunitachi are finally hitting it off steadily. However, trouble starts once again during Valentine's Day when Ikumi received a box of chocolates containing glass and became the victim several other pranks. In the end, when the person revealed himself to Ikumi, the past was unfolded.

Unconsciously jealous over what he's afraid to know, Ikumi threw a fit and said something cruel towards Kunitachi. Unable to take it, Kunitachi raped Ikumi...

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…

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.

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...

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.

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.

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.

Satou Atsushi isn't neglected by his family so much as ignored completely. Left to fend for himself, Atsushi fails to learn human speech and instead learns "cat language" and "Dog language" from the family pets. When he's eventually socialized with other children, his speech is stunted and his social graces leave something to be desired. But on his first day of nursery school, he meets a gloomy blonde with the same last name who seems to be a safe enough choice in a first friend. After developing a rather sizeable fixation with Satou Manato, he finds out that there his first friend is seriously ill and has a twin; Shuuto.

Years later, two other friends begin school and find that there are two Satous in their class too. Two Satous who, at first glance, could easily be mistaken for twins, but there's a bit more to things than it first appears...

Haizuka just wants to live a normal life, a peaceful life far away from all the trouble he's faced. But as soon as he starts highschool, an encounter with a girl and a strange creature destroys any hope of a peaceful life.

From Basement Leisure:

Kazuma is a shy high-schooler who happens to be gay, and in love with a popular and handsome guy,Ayase! A while later, Ayase befriends Kazuma, having found out that Kazuma is gay, and admits that he too is gay, and has the same feelings for Kazuma! Yet all Ayase does is have sex with Kazuma, causing Kazuma to feel insecure, will this relationship work out, or will Kazuma's and Ayase's heart fall apart?

Izumi starts high school on a low note. For some unknown reason, rumors refer to him as the notorious Izumi, a thug who loves to fight. The truth is dramatically different. Izumi is the housekeeper for his widowed father, and spends his after-school free time doing the shopping, cooking and cleaning. He doesn't have the time or energy for friends, so his bad reputation actually is useful.

But what is the problem with Segawa and Sawatari? Why are the school idols always being so friendly with him? Don't they know about his reputation? What sort of friendship do they have in mind anyway? Why does Izumi start to feel like a ham-bone caught between two hound dogs?

From Forever More:
First-year high school student Yuka happens to see his amazingly handsome neighbor kissing another man. However, he learns that the handsome neighbor is his math teacher. Having fallen in love at first sight, Yuka struggles to attract Gotou's attention, but Gotou restrains him with an, "I have no interest in kids."

Also contains a oneshot called Kabuki machi no Otoko (The Man from Kabuki City).

Han Summer (Yeuh-Reum) and Hyun Moo-Heum are very different from one another. While Moo-Heum is a brilliant, yet stunning son of a CEO of one of the most influential and extensive companies in the world, Summer, on the other hand, is a mediocre-looking girl - a plain Jane, who is just under an inescapable debt of 70 million! And to whom? It is none other than Hyun Moo-Heum! In the midst of this dilemma, a mysterious figure enters and intervenes with their lives. Could he be of any help to Summer or is he destined to make her life more complicated than it already is?

Sakura Ai, had her first love on Tokuzawa Taiyou during her elementary years. When the sweet and gentle Tokuzawa-kun transferred to another school causing Ai-chan to have a funny nickname "Granny Ai" when he left, Ai-chan tried to forget about him. But fate never gave up even when she was in high school! While Ai-chan went to her garden of sunflowers by the pool in the school, she found a phone lying on the ground. When she knew that it was Tokuzawa-kun's, she left it on the ground and ran away, knowing that the kind Tokuzawa-kun she used to know during childhood is now a frank tough delinquent, would her love for him bloom again? From Intercross: Sakura Ai has always loved sunflowers, as they appear like the sun, which incidentally also was the name of her first crush, Taiyou, in the 3rd grade. From since then, Ai has never had another love and has also become quite introverted, but after meeting a guy with the same name, somethings will begin to change… Also contains: Sugarless Kiss Ami met Kasshi-senpai when he took a bite out of her choco banana muffin. Since discovering that he likes sweets, she has given him various handmade sweets. But that doesn't stop him from having other girls around. Tsunde Renjyou Yuika and Haru have been dating for a year. Yuika is selfish and likes sweet things, while Haru is amazingly kind. But will Haru end up hating Yuika because of her attitude...