A two-part oneshot about the story of a lonely god and a troubled high school girl.

The remarried mother. After their divorce, the father who lives with his "boyfriend".
Living surrounded by such family, highschooler Mayuko is now at the height of her adolescence. Beginning from Mayuko's "runaway", intersecting various life, these are the runway story which will dye in to your heart.

A group of 5 male high school students that call themselves the funny-face group cause trouble at school with their crazy antics.

The thought of going on a field trip and taking a bath togther with Ricchan makes Fuuchan a mess.

Two parts oneshot from Comic Lily vol. 1 and 2

Newly-transferred girl, Oribe, falls in love with the most popular and charismatic boy of the school, Sagara. But, Oribe is not what she seems? The tale of the mecha girl with the heart of a maiden unfolds!

Hosaka Mao's never stood out. Her father's a washed-up rock-and-roller. Her hair reminds people of Pippi Longstocking. She's nowhere near the in-crowd. The arrival of long-haired beauty Hasekura Yokiko changes everything...

From Which Scanlations:

One day, Kengo Yagami found some of his classmates teasing a turtle that lived behind their school--and he beat them up. But when the turtle spoke, he was so shocked that he kicked it as hard as he could. Unfortunately, the turtle was actually a god, and as punishment, he switched Kengo's body with his childhood friend Mitsuka's, and their new bodies are causing both of them a lot of trouble at school...

Also includes the one-shots "Kirakira Hoshi no Ana" and "Kimi wa boku no Saboten."

From MangaHelpers:
High-schooler Matsuzaka Satou has a reputation for being easy, but one day her lifestyle of sleeping with one boy after another comes to an end. It happens when she meets the child Shio, for whom she is convinced she feels true love for the first time. Satou may seem sweet and innocent, but there is nothing she won't do to protect their life together, including committing murder. But from where did she acquire the little girl, and how long can their "Happy Sugar Life" together last?

Included one-shot:
Volume 2: White Sugar Garden, Black Salt Cage (pilot)

Short story:
A short story was released in Young Gangan 23/24 of 2016 which is referred to below as 19.5. It was later released in Volume 6 as an extra.

Reki is a high school girl that always acts cold and isolates herself from others. Yuta sitting next to Reki keeps trying to be friend with her in every way possible. However, her cheerful approach to Reki only makes her extremely puzzled and overwhelmed. At this time, the class president Maria gets in the middle of these two. Would she make things work for them or cause more troubles?

A short twitter series by @udon0531.

This boy looks so cool, so it can't be helped if I fall in love. “We've been so close ever since middle school, so now, I can't tell him I like him...” is what Akemiya feels with an unrequited love towards Iwata. But upon entering high school and becoming friends with the two popular hotties, Fujiwara and Shirotaki, Iwata is starting to get cocky!!
Iwata and Akemiya, the super popular side characters of “Fujiwara-kun wa Daitai Tadashii” presents the long-awaited super popular spin-off series that will make your chest squeeze, give you warm fuzzies, make you laugh and make you cry ♪.

Short comedy spin-off for Koi Dano Ai Dano, follow the quirky adventures of Kanoko and her high-school classmates and teachers!

From Webtoon Live and Shiro Nabi: "Welcome to Survival, 'I Am Unhappy,' the exciting game show to find the world's unhappiest person! The grand prize... is a wish granted by God!" When the victor of the game show wishes for the end of the world, God accepts this wish with a set condition: the world's end would proceed over the course of 100 days, and during that time, he is allowed to 'change his mind' only once. Oh Duk Hee, a quirky comic artist who specializes in unhappiness, is chosen by God to to make the unhappiest person on Earth happy again. With the pressure of mankind's destruction riding on her shoulders, will she be able to change his mind before it's too late? The competition to choose the world's unhappiest human?! The hybrid school fantasy action story by Jung Pil Won!

A guy decides to pretend to be a delinquent to get people to leave him alone. A girl who was a delinquent decides to act like an honor student because her parents asked her to. This is their story.

A “delinquent” who freezes up and says violent things when around women meets a small girl in the library when he's out studying. To his surprise, she tutors him, even though an elementary student shouldn't be able to. As it turns out, she's a high school student and his classmate; she's eager to befriend him. Also, surprising to him is the fact that he isn't afraid of her. Could it be because he sees her as a kid? Or does he?

Compilation of one-shots:

Watashi no Suki na Hito
The reliable class president, Megumi, is in love with her childhood friend, Yuu, who is notorious for being scary-looking.

Lovely Friendship
Hayaka and Minazou share the same interests and are perfect for each other, but when they change from being friends to dating, it somehow becomes difficult...?!

Yukimachi Bus
A story about first love in a snowing countryside.

Notebook
An honest boy healing a heartbroken girl.

Taira Capeta was a 4th grader boy. He had lost his mother when he had been very little. Although he pretended to be tough in front of his father, actually he felt lonely. One day, his father brought junk parts home from his workplace and made a racing kart. Soon, they went to a circuit to drive the kart. However, Capeta found that its frame was bent and it could hardly run straight. But, with his technique he managed the kart. Furthermore, he followed soon after the fast kart and he could nearly leave it behind. The driver in the kart was Minamoto Naomi, the champion of the East Japan Junior Kart. Looking at their chase, Naomi´s mother, Minamoto Nanako, advised Capeta to take part in the official race.

Note: Won the Kodansha Manga Award for shounen in 2005.

Higa and Nonami are classmate. Nonami is quiet and seems to get separated from friends in class. Not like Nonami, Niga is friendly and nippy. One time, Nonami must be reluctant to help Niga to study because Nonami is the most intelligent student in class...After that, Nonami start to feel feelings for Niga...

High school student Saika has psychic abilities, and is constantly tormented by people's thoughts. However, after he makes a friend, who happens to be in love with him, he finds it's not all that bad.

From Tokyopop:
CLAMP School Detectives focuses on the exploits of Akira, Nokoru, and Suoh - 3 pre-teen sleuths - and their quest to make the CLAMP world safe for the girls in their class...