Utsunomiya has been a single virgin until all the way to his 30th birthday. Then one night on his way home from work, something happened that caused a shift in time which made him go back to the past during his days in high school. There, he meets his teacher Shitara-sensei again and somehow they end up living together!?

Just your usual slice of life 4-koma... except with an alien transfer student.

From MangaHelpers:

Following the life of the student newspaper reporter Emiko, these are scary stories of experiences from Miyako High School :-

Ubawareta Shinzou (Stolen Heart) -- The school's mystery club sees the dangerous consequences of an innocent promise concerning heart donation after death between two friends.

Kyuuketsu Men (Bloodsucking Mask) -- A girl who wears a demon mask from a shrine for a bad-luck-banishing drama club party ends up unable to remove it.

Dokuga (Poison Moth) -- The science club leader creates a serum to preserve dead bodies perfectly, but it may have other unpredicted side effects.

Henshitsu -- A couple take shelter from a storm in a strange house with a secret that might prove to be deadly.

-- These stories and many more are found in the two volumes of Kyoufu. [tethysdust]

If you enjoy the world of the younger sister who continues, there will be only one word that comes out! Then everyone together ... "Sister is good!

One night, Keiichi Yukihara is visited by a girl in his dreams. The girl tells him that the next day, a timid girl with bangs will talk to him and that he must befriend this girl. The next day, he does exactly that and finds out the girl's name is Michika. What he doesn’t expect though, is that the girl talks to a doll she carries with her… A doll that has a remarkably similar appearance to the girl that appeared in his dream. What is the mystery of the dream girl and why must he befriend Michika?

"To Love, or not to Love"
Juliet Percia and Inudzuka Romeo are archenemies. They lead two high-school dormitories the "Black Dogs" and the "White Cats" from two rivalling countries. Both factions are dead set on defeating the other to gain control over the island they have to share. Beneath the feuding exterior, however, Percia and Inudzuka long for love and peace for their budding relationship...

Set 16 years after the "Law for Public Order and Morals in Healthy Child-Raising" banned coarse language in the country. Tanukichi Okuma enrolls in the country's leading elite public morals school and is soon invited into the Anti-Societal Organization (SOX) by its founder, Ayame Kajō. As a member blackmailed into joining by Ayame, Tanukichi ends up taking part in obscene acts of terrorism against the talented student council president Anna (for whom Tanukichi has a crush).

Saori loves playing music; she loves it so much she even imagines herself playing to a large cheering audience… that is until her imaginary concert is unexpectedly interrupted by a bus being driven by her best friend, Tomoka! This is a story that looks into the past memories of Tomoka, as she drives around picking up all the magical characters that influenced her childhood. This is a beautiful story that shows us the true meaning of friendship!

A boy got forced to go through a heart throbbing penalty game.

This is a story that takes place in a future not so far from now, in a world where animal ears have become a huge part of fashion. Brand new high school student, Midori Nonono finally convinced her parents to let her wear the animal ears she always dreamed of having. However, as soon as she puts on her bunny ears, the libido of a rabbit overtakes her and her sexual desire goes crazy!
This is the start of Nonono's messy animal ears life.

From Summer Rain:

Although Koharu is a little taller than the average person, she's a 15-year-old girl who lives a much simpler life than the average person. Having no experience with love, she thought she'd spend her days peacefully with her group of ordinary friends. However, a destined encounter will change Koharu...!!

The story begins with Izumi Hayato running to be student body president. But when a beautiful girl swings in promising the liberalization of love while flinging condoms into the audience, he ends up losing to her and becoming the vice president. At the student council meeting, the newly-elected president invites herself over to Izumi's house, where she promptly announces she is to become Izumi's wife thanks to an agreement -facilitated by alcohol- made between their parents when they were only three.

There are some humans capable of using magical power to manifest their souls as weapons and control forces beyond normal comprehension. These people are known as Blazers, and those who are recognized as such can undergo training at academies to become Mage-Knights. Ikki Kurogane is an aspiring Mage-Knight, despite being considered the worst student at Hagun Academy as an F-ranked Blazer—the lowest rank possible.

One morning, he accidentally stumbles upon Stella Vermillion, a visiting princess and A-ranked Blazer who has just enrolled at Hagun, in a state of undress. As a result, she challenges him to a duel where the loser will be the winner’s slave. It seems like a surefire win for Stella, but could there be more to Ikki than meets the eye?

The favourite committee member, Chihiro. The problem child who always skip, Kisaragi-kun gets himself involved by the teacher, and the relationship changes..!! Chihiro was very troubled by the ill mouth and uncooperative Kisaragi, but...!? The favourite committee x handsome delinquent, a heart throbbing school love starts!

After an accident that made him unable to distinguish people’s faces, the main character is shocked when he sees the new transfer student, and thinks he’s found the one.

A comedy using perverted themes. Mainly between brother and sister.

This love relationship is only through smartphone technology and how the characters fight to keep the relationship safe. Technology simply plays a supporting role in this relationship and our protagonists are two people who are shy in love.

There's something unusual about my class. Our beautiful and perfect angel classmate, Amane, just died. That's why everyone is doing a “funeral” for her. Everyone seems to be scared but did not say anything. I'm sure they are hiding something. After all, before she died, Amane said something strange. Hey, don't tell me, there are traitors among us? Well, let's hold a “class meeting”! No one should ever leave the room before we know who's behind this...

"Twins" - Two children that develop in the same womb and are born at the same time, Even though we were raised in the same environment, even though... "When we were born, Hinata took even my portion of the nutrients... Those nutrients, I don't mind giving them back to you, Haru?"

Saya is an average school girl in every way but one: she's got a HUGE crush on her older brother! She's never been able to raise any flags with him (mostly due to her habit of beating him to a pulp whenever she sees him), but one day, she wakes up in the body of a cat that he brought home! Could this be her chance to make her beloved older brother fall for her?