From MangaHelpers:
Namidare Rekka has a very unusual birthright. After his 16th birthday, he will be drawn into many different stories. Each story has a heroine, and each story depends on him to be the hero. On his first day of high school, a strange uniformed girl that only he can see shows up. She claims to be from the future, and claims that his rescuing of many heroines is going to cause serious trouble for the future.
It's not long after this encounter that his troubles begin. His childhood friend Satsuki invites him somewhere, possibly to confess her feelings for him. However, before she can, she's kidnapped! Rekka wants desperately to help her, but he finds himself being tossed into various sci-fi and fantasy worlds, each with their own heroines in trouble. Will he be able to get back to Satsuki? Will he be able to save all the others? How can he really tell the consequences of his well-meaning actions?

Shouta, a 25-year-old NEET, is mocked by his former female classmates who've all become successes, at their class reunion. A mysterious incident at the school pool throws him back in time and lets him deal with those same classmates back when they were fifth grade girls.

From MangaHelpers:
Summoned into an alternate world of Alayzard, Ousawa Akatsuki helps defeat the demon lord, brings harmony back into the world and, under the demon lord’s last request, takes the demon’s only daughter back into Akatsuki’s own world.
It turns out that being teleported into a different world is somewhat of a common occurrence back home. Those who return often come back with the power to use magic. So a worldwide organization, fearing people like Akatsuki, created Babel, a school to teach and keep tabs on the magic users.
Akatsuki is able to bring the demon lord’s only daughter into Babel as his sister, Ousawa Miu. A new chapter for Akatsuki is about to begin--this time, in his own universe!

Tooru Sawada not only goes to the same school as his young aunt Sugako but has to live with her under the same roof! Somehow Tooru always ends up being dragged into his beautiful and mischievous aunt's pranks and shenanigans.

In a flash, Akihabara, the legendary Otaku neighborhood, was teleported to Fairleaf, a country in a fantasy world of spirits and magic. After an investigation, Akihabara's culture and technology spreads throughout Fairleaf, sparking a cultural revolution.

Brought along for the ride, Kubo Toshinori runs the Galge company "Eternal Soft" in this new world. Alongside his cute Beastfolk assistant (and PR manager) Monica and his half-elf Potion-binging Programmer Iris Ohkawa, Kubo and Eternal Soft continue the constant struggle against deadlines, Twitter trolls, and software bugs!

Taro Kajiura and his friends from a research group at Tonan University embarked on a trip to Ikishima Island in order to pursue the origins about Princess Kannon. At the same time, the villagers of Ikishima were holding an annual festival in which outsiders were forbidden to participate in for over 400 years. The consequences for breaking that tradition were much more severe that any of them had imagined...

The day a young boy was born was the day that the legendary thief died. The many battles that revolve around the treasure left behind by him. Here, the curtains are pulled and the story starts.

The heroes of the three kingdoms' war have been reincorporated in high school girls! Loyalty and hostility concern love in this world...? Wei, Wu, Shu, during the Three Kingdoms period they were warriors who fell in the mind and fell down in the chest... But what do they do in Japan?!

It tells the life story of Hayato Heiwajima ordinary guy occupation is the main successor of his grandfather and Heiwajima industries, the Maid Hatoko Heiwajima and close relative, is responsible to teach you how to deal with females and is not so easily fooled. The problem is that her teaching methods go beyond the ordinary.

A speck of dust can fill an ocean. A blade of grass can destroy the sun, moon, and the stars. A flick of a finger can turn the world upside down.

Groups of heroes rise, and innumerable clans stand together. Various saints fight for power as the entire world falls into chaos. I ask the boundless Mother Earth: Who decides the ups and downs?

A young man walks out of the barren wilderness, and everything starts from there…

In both middle school and high school, Kawashima hadn't had any luck with girls, but this is the day that a miracle encounter came to him! In the apartment where he moved, there was a high school girl living in his neighborhood and in addition to that, she is living alone! In a situation that any man will admire, Kawashima's tension is hyped up. However, there was also a odd part to it, like she likes to drink beer. What is her identity? It's a little bit ecchi JK comedy!

Hayate Ayasaki, 16, the world's unluckiest boy. Working hard as a child for food and school fees, his unemployed and indebted parents sold him to the yakuza for his internal organs. After temporarily escaping the criminals and contemplating the benefits of a life of crime, he was saved by a wealthy young girl; who now employs him as a live-in butler.

Spin off of Sekirei. Takes place 365 days before the return of Musubi. The tagline is "One year with his girlfriend gone. One year until she returns."

The protagonist, Kotaro lives together with his 3 sexy step-sisters

From Fallen Syndicate:

The Juuza. That is the name given to those of the 13th Zodiac: the cat people. Seen as a vulgar and contemptuous race, they live a life of seclusion away from human eyes. However, as the end of the Han Dynasty draws near, the rise of the Yellow Scarves has thrown the land of the Three Kingdoms into turmoil. As armies converge, a young Juuza woman named Kan'u and her village are forced out of their peaceful lives as Sousou and his punitive force press their way into the village.

The story follows Arcana Famiglia, a self-appointed organization with mysterious powers that has protected a small Mediterranean island from pirates, foreign countries, and other threats. The only daughter of the family's "Papa," Felicitá, will be married to the next head of the family in two months — and the successor will be decided in a competition that Felicitá herself will take part in.

Jin-Woo gets a new beautiful mom who is 10 years older than him.

When Mikoto was little, she first heard the voices of plants. She also gained flower markings on her face and body, as a sign of her connection to them. Unfortunately for her, she was brutally teased and bullied, both for the markings and her claims that she could hear flowers talking. By the time she was in high school, Mikoto took to wearing clothes specifically designed to cover everything, but she still couldn't escape her classmates' bullying.

One day, a strange and exuberant transfer student, Aozakura Yuji, appears and takes an interest in Mikoto. He's determined to start a flower arrangement club, but with a twist: he wants to photograph beautiful girls arranged with flowers. He first pursues Mikoto, both for her beauty and because he bears the same flower markings as she does. After he photographs her for a promotional poster, everyone at school can see the beauty of Mikoto and her flower markings. Will Aozakura's flower arrangement club succeed? Is this the start of a new high school life for Mikoto?

By aquamarinep:
The world has became a place dominated by males. Women are virtually extinct with their number-count in the hundreds and the youngest of the them in her forties. It has been long accepted that a wife, being a gender so rare, can have multiple husbands. Sex change to satisfy sexual desire is a growing phenomenon, although is still looked down upon by society.
In such a disordered place where she is the only girl, Ho Su awakens.

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