I couldn't kill my assassination target because he's too cute, so I became his girlfriend instead.

From MangaHelpers:
An exorcist has just finished defeating a demon, when one comes falling out of the ceiling. However, she's nothing like the sexy, dangerous demon he had just faced. She has no horns, she's in ragged clothes, she's starving, and despite the fact that she claims she's here for his soul, it's clear that she's little threat. Instead of killing the demon, the exorcist is moved by pity to buy her some food. Now she's determined to tag along with him, eager to do anything she can to be useful.

The name of the hero is KageKon (Kagechika-Shinobu) and her missions come from the student council president who is her lover as well. KageKon's role is to solve the various problems of the school while keeping her identity secret.

Makoto Okazaki is your run of the mill high-schooler, a perfect bullying target and a closet pervert. One night he decides to return a DVD to a friend of his and ventures out into the darkness. He notices a person on a nearby rooftop. The person lunges at him before he is able to make sense of this, and bites into his neck, drinking his blood. The attacker stops. At this point Makoto notices that the attacker is a beautiful girl. She asks him: "Do you want to die or become like me?" He decides to live...

Bossa goes to an all-boys school, and like that in itself isn't the worst possible scenario for an adolescent boy, his classmates have recently started playing a game where the objective is to make the opponent aroused before they can do the same to you. Bossa finds it all disgusting and pathetic, but his self-proclaimed best friend Akiyama is determined to "defeat" him.

A romantic comedy with a busty hafu blonde onee-san teacher and a hard-working scary delinquent.

This is a series of 4 one-shots by Asou Mikoto that all have a common theme of words and language.

Kotonoha ~Usuyou no Tsukebumi~ :
Maeda Kotoha joined the calligraphy club at her highschool b/c she was impressed by the club president Fujisaki's demonstration. Unable to gather up her courage to confess her feelings, he graduates. Feeling regret, Kotoha decides to write him a letter using a brush and traditional paper...

Kotonoha ~Ningyohime no Kowairo~ :
Manabe, a cool ice queen type of girl, in Fukazawa Tatsuhiro's class joins the swim team even though she can't swim. Intrigued, Fukazawa decides to teach her, but wonders why she wants to learn so badly...

Kotonoha ~Tenjousajiki no Naishobanashi~ :
Mihara Ritsu is a playwright for her school's drama club. Nakajima is an underclassmen who joins the club because he was moved by the lead actress Seto Miyabi's words in the final scene of last year's production. This year, Ritsu must write a play that stars both of them, but as usual, writing does not happen easily...

Kotonoha ~Shijin no Koi~ :
It all started when Sako accidentally picked up Kumazawa's book of poetry and secretly read what she wrote. A lot of it was humorous, but some poems were serious, particularly the ones that poignantly expressed her feelings about a certain classmate...

From Viz:

Hanayu Ashitaba is the daughter of the celebrated Patisserie Ashitaba, but all she wants to do is be a sushi chef. Hayato Hyuga is the son of the prestigious Sushi Hyuga, and all he wants to do is be a pastry chef! It's love and leftovers at Oikawa High School Cooking Department as these star-crossed gourmands do their best to reach their cuisine dreams!

From Chibi Manga:

Even if she studies hard, Tsugumi can't reach a good grade. She is also complexed by her height. But then, someone started cheer her secretly...

Hinako had always admired and observed this one boy in her class. She admires him so much that she, at the very least, hopes she has something in common with him. Little does she know they're more similar to each other than she thought, for better or for worse.

“My feeling for Daichi should not be known... forever."
Mihiro has been secretly liking his best friend, Daichi, a clumsy high-schooler who has bad luck with women. When Mihiro got confused with his relationship with Daichi, his upperclassman started to approach him. But why does Daichi act like he's jealous? Even though he supposed to be head over heels towards his girl crush...

Even though Mitsuru has a pretty face, he is followed by rumors about his promiscuity. In reality, he goes out night after night looking for strangers to have sex with. Rumors are flying around school that he is a flirt, but this is convenient for Mitsuru who doesn’t want to make friends with anyone. However, new transfer student Hasegawa is irritated by this attitude and he begins to follow Mitsuru around. Will Mitsuru’s loneliness be revealed as Hasegawa crashes into his life and stirs up his heart?

One-shot of a cute girl with snakes for hair.

High-schooler Saionji has moved into a boarding house with a really cute young landlord named Sakura, who also attends his school. Though it's really near the school, the place is pretty broken-down and all the other tenants are strange women. They include little Hana, who wears costumes in public, a sloppy, lazy teacher, and his slightly uncivilized schoolmate Akira. Living in the boarding house does not help Saionji's reputation at school, but he has a huge crush on the landlord. Will he be able to handle living with all these bizarre women, and somehow win Sakura's heart?

A romantic comedy about a boy and his social media rage; a story of social media and the crossing fates of a young man and a young woman who were never supposed to meet. Say hello to Daichi, a.k.a. Mr. Harmless. Because of his compulsive need to be liked, he never makes waves and maintains an easy going attitude. So easy going, everyone thinks he's a dud. But online he's a stud! His angry otaku online persona has garnered him thousands of followers! But real life and online life are two very different things. A lesson he's going to learn the hard way!

The plot is about Japanese teen Yamato Hibino, who is sucked through a time warp into the past, where the dinosaur army of the Dragonia Empire threatens the world, and Queen Aira of Mu needs Yamato to help her fight back with the aid of the stone-made guardian God Mazinger, which looks suspiciously like a giant robot.

Niina Keito is always surrounded by girls who're into casual relationships because of his showy looks and "playboy" demeanour, but he's actually a pure-hearted shoujo fan who's never even had sex before! On the other hand there's Takizawa Ryou, who's the picture of a studious, courteous prince in front of the girls but is secretly a mean-spirited guy who doesn't care for them one bit.

These two polar opposites are newly stepbrothers and therefore forced to live under one roof, but this, as well as the fact that their true personalities are completely different from their chosen images, are the two secrets they've both agreed to keep for each other.

But one day, quite out of the blue, Ryou kisses Keito, saying "Choose me. I'll love you for who you are"!?

From Paperdolls Project:

The new public health doctor-teacher that has everyone talking about is my childhood friend. He, that is ranked "elite" in looks, body and intellect is actually a big pervert! He harasses me daily and is extremely overprotective. This has caused me to have no dating experience let alone a boyfriend and I am already in HIGH SCHOOL! But lately, why is this perverted person is causing my heart beating so fast? A funny comedy between an older assertive childhood friend and the girl that is determined to not fall for his trap!

Just a short one-shot manga that was posted by the artist on Twitter.

DMG:

Love is found in the strangest places and with the most unexpected partners. The men (and cats!) of SENTIMENTAL GARDEN LOVER burst into heart-throbbing bloom!
A scruffy stray cat wishes for big hands to hold an abused man, and a cute kitten begs for speech to comfort a broken-hearted stranger. Wander further into the garden, and you'll find close siblings upset by a love rival; a jaded delinquent flustered by a trusting bookworm; an evasive, glasses-hating man; and a president eager to find a weakness in his perfect secretary.
For both cat and human, the quest for love is here!

1. Sentimental Garden Lover
Fuji is in love with Hiro... so much, that he feels no matter how far he stretches his arms, they could never encompass Hiro. Everyday he watches Hiro's abusive lover, wanting to rescue Hiro, but there is nothing he can do because... Fuji is a cat. When Fuji miraculously acquires a human body, and Hiro finds him, the past interferes in their future.

2. At Home Holiday Lover
Shima, the other cat, quietly lets go as he watches Fuji and Hiro and begins searching for a place to call his. He literally falls into the arms of love when he passes out from hunger and lack of sleep and tumbles into a man's bag. Taki brings Shima home and feeds him milk, breaking through Shima's defenses. But Shima finds himself in a painful love again, only able to watch desperately as Taki and his ex-lover (who is also named Shima) try to let go of one another.

3. I'm Home!
When Fuji tries to make Hiro coffee but fails (he's a cat... duh.) he decides that doing the dinner shopping is an even better idea. He gets chased by a stall owner and needing a place to hide, he finds a lovely open bag sitting there. And that bag belongs to none other than Taki-san! Fuji is reunited with Shima, but neither one knows where Hiro's house is...

4. From the Heart
Shigino is a delinquent who's always getting into fights, and on top of that, he gets blamed for things he hasn't done... but everyone has already made up their minds, so what's the point of denying it? One night, bloody and being chased by cops, he stumbles into an old bookstore. The owner, Sakurai-kun, is a bubbly guy who starts talking non-stop... but Shigino finds himself coming back again and again. For once, he hopes someone won't find out what they say about him... but what happens when Sakurai does?

5. Right Palm, Left Palm
They're brothers. That's why they are so close, that's why they hold hands, that's why they kiss... but why is it that they have been told so many times "Your love is strange."? When a friend says something to him, the older brother begins to understand that maybe he can't let go anymore... and what people mean by that statement. But what if Naoto doesn't want his nii-san to let go?

6. And I Come to Like You
When Oya's junior, Kuze, confesses to him a week after Oya was dumped, things get complicated. Oya likes Kuze, but can't accept the fact that Kuze wears glasses.... because the one who dumped him also wore glasses. Oya comes up with a stupid excuse about hating glasses... but Kuze doesn't believe him?

7. I Want You to Always Smile
The President has a problem: his secretary. Natori is so neat, and organized, and on top of things! Determined to bribe him, the President tries to find dirt on Natori... but he can't - that is, until he sees Natori looking happily at cakes in a bakery. Maybe, with a little bit of cake, the President can find out why his secretary is so dedicated.

+ Extra.
Extra about Shigino and Sakurai from chapter 4.