This 4-koma style manga features Yoshiko, a genuinely stupid girl (she can even manage to get all 0's on multiple choice tests). She hangs out at school with her childhood friend, who she claims to like, and he has to put up with all her ridiculous behavior!

From Tokyopop:

Daphne in the Brilliant Blue take place in a near future in which the remaining population lives in underwater cities, with waterways as streets. Years ago, while conducting underwater experiments, all contact with the surface was cut off. With the remaining human population now living underwater, The Deep Sea 9 Cities Association represent the last hope of mankind. Ai Mayuzumi is the daughter of the head of the research lab, and is an expert water jet bike driver. When the terrorist group Error, attacks the city, Ai becomes involved with the counter-terrorist group Stelnas, comprised of an all-female team, and led by a girl named Kei, and asks to join them. The group initially resists her efforts to join, but a surprising "gift" that Ai possesses, along with the way she handles herself during a kidnapping attempt, eventually sways the opinion of the members of Stelnas.

Renji is a photography college student., just now living on his own in Tokyo. He sets about seducing a classmate, and then things start to go in direction he didn’t expect.

Due to a request, the genius Dr. Sumiko developed an「AI boyfriend」.
Sumiko is pleased with her success, but the AI boyfriend who started will recognize her as「girlfriend」...!?
Initially, Sumiko rejected the AI boyfriend.
However, being subject to his constant love gradually leads her to acknowledge him...
A hot topic on Twitter and pixiv! A love comedy between a handsome AI and an unpopular woman begins ♡

"I can probably no longer return from being drawn to such a world."

1-2. The Which Is Love?
"Sheesh, he’ll cry over any type of love. I really can’t understand it."

Nonami ended up having to comfort the heartbroken Hino after he was dumped by his girlfriend. Even though Nonami thought he couldn't comprehend it, he was charmed by Hino's honest feelings. A heartrending story of sweet youthful gravity.

3-5. Sen no Yoru

6. Love and Goldfish

7. Sen no Yoru Extra

1. Ai, Daro. 1
Yukihiro and Takase are salary-men working together in the same company and whom share a physical relationship. However, Takase's easy-going nature and loose relationships with women makes things complicated for Yukihiro.

2. Ai, Daro. 2
Yukihiro is moved to a new section of the company - located 3 hours away from Takase. Can their newly formed relationship stand against this sudden separation?

3-4. My Eyes & Your Eyes
Kamihara has never felt feelings of 'like' or 'love' towards another before but doesn't like it when Nakahashi points it out. Nakahashi is also of a similar state of mind, so when he suddenly confesses Kamihara finds it hard to reply.

5. Only Angel Knows
Chiaki has always had a weakness for abandoned creatures, so when he see's a man getting beaten by a gang he intervenes and ends up taking the man home to treat his injuries.

Gomennasai.
A student hooks up with a woman for casual sex. They have an awkward meeting sometime afterward, in his classroom... because she's a substitute teacher.

Bousou Kiss

"...Gokko"
Brother and sister. A couple plays an incestuous game where they do perverted things to each other until one gives up.

Otoshigoro

One Step

Ferris Wheel
Sudo-san has a lover, who is two years younger than her, Takahana-kun. After receiving the news that Takahana-kun is going to be transferred, she thinks about how to work out their relationship.

Yume Musubi to

Hakuchu Yamu

Yoshi x Yoshi

Only One
Izumi Taeko is a weird and flighty girl, rumor has it you'll only need a coin to get your way with her, but is this true?

- Animexis

Reset

Sajimiya Reiji and Mijou Yashiki are partners who use their "Death Guns" to hunt a group of vampire-like beings known as "Artemis", created due to a natural disaster that occurred a century prior to the events of the story. When a group of Artemis that calls itself "Pleiades" begins to attack random humans and convert them, naive newcomer Takao Iota teams up with his two more experienced co-workers to try and hunt down the ones responsible.

From Pink Rose Scans

Mizutani Yoshiki is a 21 year old working as an assistant director for TV shows. His friends from back in high school are all jealous because they think that he's able to rub elbows with celebrities but in reality, he's so far down the TV industry hierarchy that he's more the resident lap dog relegated to doing everyone else's dirty work.

One day, he gets assigned to help out with filming for the latest "it" drama. The lead female actress turns out to be none other than Fujiidera Mitsuko, the girl he had a crush on back in high school who's now become one of the hottest rising stars in the acting world.

As he quickly finds out though, she's nothing like the shy, quiet girl he knew from back in high school. What happened to her for her to have changed so much?

Includes another story
・「My dear B・F」
Ever since the car accident that ended her dreams of becoming a short track athlete, Yumi's been struggling to pick up the pieces and move on. One day, a mysterious boy who calls himself "Jiro" crashes into her in the school hallway. They quickly build up a close friendship---but there's something strange about him that she just can't put her finger on. Who is he really?

Collection of oneshots:

1) Compass of the Heart
Miyahara Yoshimi is troubled by the gaudily dressed host who always comes into the convenience store where he works. But when Tsumagi Makoto passes out in front of the store, they become friends.

2) The Difficult Couple
Continuation of chapter 1.

3) Singing Stray Cat
Prequel to chapter 1.

4) From Rain
Accidental death, murder, guilt and punishment affect a man, his younger cousin and the cousin's best friend.

5) Summertime
When Haruhiko's summer plans with his girlfriend fall through, he ends up shuffled off to visit his cousin near the beach. But cute waiter Nanami looks so shocked to see him, have they met before?

6) As Long As There's Love, Age Doesn't Matter
Tomo wants a little affection from his cold older lover Reiji, and he's not speaking to him till he gets it. After two weeks, is it all over for Tomo and Reiji?

1) Ai ga Aru kara
An insatiable lust for men has landed Matsuzoe with his fair share of them. However, after sleeping with a new and younger acquaintance, he’s gripped by an inexplicable sadness.

2) Re:Cycle
Tomo picked up a stray cat even though it was against his apartment's regulation and got kicked out. Luckily Yuusuke suggests that they live together instead.

3) Kemono Dou
Even though Kaji has no problems finding transient love, he is looking for more than just a one night stand.

4) Omoeba Tooku e Kita Mada
It is almost dawn and the taxi driver picks up a passenger that tells him "Let's go to the beach".

5) Dourakuteki Matomo na Nichijou
Kousaka is fretting about his workplace; his boss seems to be completely nonplussed whether the cafe will go under.

6) SWEETOGRAPHY
Yamanobe looks like he is leading the charmed life but Itou slowly learns that there are many things that he can't exactly talk about with others.

7) Hana Aogu
The heir to a flower arranging business is being pressured to marry soon. On the eve of the marriage interview he meets a man who makes him question his duty to his family.

8) Tooku de Mikaketa Ano Hito wa
Matsuzoe (from chapter1) sees Masaki by chance on his way to his latest conquest's place.

A manga picking up Yoshinaga and Takao's story a few years later. Takao, now a college graduate, starts up a small business with ex-classmates. However, the life of an adult is not what be expected it to be ultimately leaving him with his newly found inner turmoil.

1-4) Ai ga Love Shite You nanosa
Oono is unable to properly do his uniform check job because his adoration of Takeuchi distracts him, and Takeuchi mistakes this for Oono hating him and is sad at the idea of being disliked by the model student. Thus, Takeuchi is relieved and willing to reciprocate when he finds out that it isn’t hate but instead love that makes Oono so very awkward around Takeuchi.
from hazukashiikedo

5) Shiritsu Koukou Hetarebu

6) Nare Somehen

From Yaoi Is Life:

There's Kiyohito, who continually cheats in whatever relationship he is in. One day, while he was sitting at a bar, a man named Hisashi comes stumbling in. Hisashi's got less morals than Kiyohito, but despite being a crazy guy, Kiyohito can’t bring himself to hate the guy. When they are together, everything feels good...?!

Hitoshi Kobe is a terrible student and an even worse athlete ... though he does have an incredible talent for creating Artificial Intelligence programs. Thirty is his best artificial intelligence program yet -- and, more important, the only girl who will talk to him. Hitoshi's life is forever changed when a freak accident brings Thirty to life ...

From Condensation:
Toujou Souko attends a Catholic high school for girls and spends most of her days ditching class and trying to hook up with guys. She's in a hurry to fall in love and often gets into trouble. Ueda-sensei is Souko's homeroom teacher and all the girls idolize him on campus. He thinks Souko's a good kid and is looking out for her best interests... Yet he never meant to encourage her to try and seduce him...
What begins as a passionate affair becomes a true and undying love... Ai Girl is an angsty love story loaded with melodrama. It should be noted that this series has adult themes and high smut content.

From Wild*Hope:
Honoka's fiance disappeared the day before her wedding, leaving her heartbroken and completely sceptical of men. Oshiro wants nothing to do with women but needs a place to stay. Somehow, they end up living together. Honoka also asks Oshiro to pose as her newlywed husband...

Also includes one shots Pure Love and Springtime Sleep Remedy.

They met. They kissed. They parted without a word. The next day, he turns up at dinner with her parents... And he's her father's stepbrother! Seven years her senior, and her uncle by marriage alone, he has been trusted with the duty of living with her as an "uncle" while her parents are working overseas for two years. Even though they're not blood-related, can Mao decide to love him and go through the struggles to be in love with him?

From Midnight Scans:

A quiet girl falls in love with a fourth year ikagu club member, Koushirou-san, who is a kind, serious, and charming person... But then... why would he...!?