From AnimeSigma:
One day while Shirou was delivering a secret weapon to his colleague, he met Amane Mao, a super strong girl who is capable of lifting cars. Before they knew it, an ERROR, a monster that struck Old Tokyo 14 years ago, reappeared and started on a rampage. While he was arguing with his colleague over the use of the super weapon to save civilians, his colleague was blown away and died. Faced with death, Shirou had no choice but to combine with Mao with the super weapon and destroy the ERROR.

Kirika Hijiribashi is the Executive Committee Treasurer managing a high school's student council budget of 800 million yen. She is also the only committee member with an additional title: Student Council Detective. As shy as she normally is, she is able to sniff out amazing solutions to bizarre cases.

Hikage Makimura transferred into the same high school to escape living in the shadow of his brilliant older sister. Suddenly, he finds himself tricked by the mentally and physically strong female President into not only joining the Student Council, but also becoming Kirika's assistant, to the dismay of them both.

Can he create happiness for himself, much less others, in the midst of money-motivated intrigues? Can he make a name for himself when his own name is given to the the lop-eared bunny somehow filling the PR position, a rank higher than his own? And when will people stop asking him to betray a position he never wanted in the first place!?

Man's true worth is to entertain the beauties of the world. Summoned in a different world called Romless, the college student Simon Claud (or Shimon Kurando) aim about women, treasures and adventures runs around the labyrinths, deserts or cities. Young ladies, princess knight, beast girls, elves or woman assassins, I'll get them all! The most absurd dark fantasy is now unveiled. Men must adventured until the death!

One day, when she was chewing on some bread she'd gotten for her snack, the thirteen-year-old Dahlia Pesteros suddenly remembered her past life. This was the world of a tragic otome game where the characters went crazy, and I was born as the younger sister of the future's greatest villain! At this rate, there would be no solution. The household would be eliminated, and my head would get cut off. That's why I have to get out of this household as fast as possible! "I'll make him let his guard down and then I'll escape!" It was going well up until I got rid of the relative who was aiming for our household, plus others such as the snake-like Emperor, and received Brother's approval... "I want to dance with Dahlia. What's the problem?" "Unfortunately, my younger sister is shy." "I said that I like Dahlia the most!" Somehow, I tamed my brother too much, and now the strongest characters in the world are obsessed with me!

The strongest Hero in history, Nakamoto Keisuke.

He was summoned to another world in the spring at the age of fifteen years old, and when he successfully defeated The Demon King, he was already thirty-two years old. He had finished his role in another world and returned to Japan, but the reality that had been waiting for him was, “Middle school graduate with seventeen years of blank period” label. He couldn’t find a decent job and had no choice but to spend his days working part-time.

Before such a Nakamoto, a beautiful girl who self-proclaimed had come to return the favor, appeared. “I’m the reward for Hero who had defeated Demon King”, said Angelica, a girl who came from another world that persistently tempted Nakamoto to make her his wife. Together with a high school girl who looks like Elsa, his beloved girl that he lost in another world, Nakamoto with his cheats skills got caught in a harem life.

After the carriage she had embarked upon crashed, Stella is saved by a tall dark and handsome stranger and brought to the mysterious mansion surrounded by poisonous roses in which he lives with three other gorgeous men. However, with no money left, Stella is forced to work as a maid which will prove dangerous for her because she is yet to find out that all four men are actually vampires!

Mythical Abode Mountain, Cloud’s End Cliff, the most dangerous of Azure Cloud Continent’s four deadly areas. Cloud’s End Cliff’s base is known as the Grim Reaper’s Cemetery.

Over countless years, the number of people that have fallen off this cliff is too high to count. None of them, even three stronger than god masters, whose power could pierce the heavens, have been able to return alive. However, a boy that’s being chased by various people because he alone holds a priceless treasure jumps off the cliff, but instead of dying he wakes up in the body of a boy with the same name in another world!

This is the story of a boy wielding the Sky Poison Pearl, cultivating the strength to oppose heaven and earth, a lord overlooking the world!

The story of the former hero Loki and his time working at an onsen with his monster co-workers!

In a fraction of a second, an university student, Kashiwagi Yuuya was summoned to another world and came back. Time didn’t pass in Japan, but Yuuya has completed the quest as a hero in another world and successfully returned. But to his surprise, he still retains his powers as a hero. Thus started the unordinary life of a hero in present day.

The popular Isekai but not Isekai web novel is now in manga form!

WN Raw: https://ncode.syosetu.com/n7294dm/

The wizard Haru spent his days being abused by the hero, his childhood friend Leticia, when one day while being scolded he thought to himself, "This is no good". And thus began Haru's adventure to regain his true self! The curtain unveils on an other world "redo" fantasy life!

"I'll turn the tables on the main character!"

Yohei Mochizuki, a new student at a [geist] user school, was bullied by his classmates because his geist partner, a [Goblin] by the name of Gobubi, was weak and ugly. However, one day he discovered a "wiki" and realized that he was living inside a game world, and his situation changed for the better! "No more tears. Let's take revenge on the main character together."

Yohei took full advantage of knowledge about the game to evolve Gobubi into the strongest natural beauty! With this, he can look back at his classmates and stand next to the senpai of his dreams! But just as he was finally able to obtain happiness, but then I was suddenly challenged to subjugate a domain boss by a beautiful foreign exchange student...are these problems that happen as you get stronger?

This is the fairy tale story of a boy who resists fate as the game's loser character and the weakest [Goblin], who together, aim to become the strongest!

Felmenia Stingray was a genius magician. She quickly became the most distinguished magician of the Astel Kingdom after her discovery of white fire magic, which had the power to burn anything.

However, the world is in peril due to the Demon King. The kingdom's court magicians perform a summoning ritual for heroes and bring forth a hero and two youths, a boy and a girl. Unlike the girl, the young man refused to fight the Demon King alongside the Hero and demanded to be sent back to his world. The kingdom, angry with his behavior, locked him away.

Now Felmenia stands before the same young man with her strongest magic, the white flame, being completely useless and asks who he is. It was already obvious to her that this man was far stronger than she was. To this he simply responds.

"Yakagi Suimei, a magician."

From AOC Translations:
Tsukishiro Nina moves to Ruberia, a small country surrounded by the ocean and roses. But suddenly, she was bitten by a young Loup-Garou, a beast that is said to only exist in legends. Once bitten, Nina herself turned into one of them and was forced into "Abigaile" an academy prison on an island where all the beasts are exiled to. What cruel fate awaits the pitiful Nina...!?

Alexandra is the duchess of the Kingdom of Tarraconensis. It was only the day before the absolution event that she realized that she was the villainous daughter of an otome game! It's clear that she'll be denounced and her engagement will be broken tomorrow.
But I don't want to be condemned honestly! I'd rather show my eyes to the people who despised me! With only 24 hours left, Alexandra begins to make a breakthrough in her desperate situation.

From ShoujoMagic:
On Kabuchi-jima, an island ruled by Princess Kaguya, ten children were raised as sacrificial victims. Several of the children thought they had escaped their fate when they escaped the island. But nearly a decade later, the kids are still dying in the order and at the time they would have as sacrifices... Their only hope now is to reunite and return to the island to seek out and destroy the source--the legend, the blood-lusting Moon Princess--before time runs out.

In 2002 Kaguya Hime received the 47th annual Shogakukan Manga Award for shoujo.

College student Otonari Otoya is a boy who lacks self-esteem and dreams of being reborn into a different dimension. One day while playing a [video] game, he accidentally clicks on an ad, and trips into another world?!?!
He's surprised but delighted, until he realizes that something's strange. A whole group of guys are treating him too kindly, almost like he's a girl! Could it be that the world Otonari was transported into... is an otome game?!?!

A veteran adventurer was preparing for his retirement when his former disciple returned to the village, intending to recruit the old man to his party. Filled with regret due to an incident that happened in his first party, the old man rejected his offer. Being affected by his disciple’s adventurous spirit, the old man leaves in hopes of reigniting his long-lost dream, to become the strongest adventurer that ever lived.

Ruu Brandel, a genius wizard with a talent for thousands of years. One day helped a beautiful aristocratic daughter, Franc and was to be assigned to “Magic Girls' Gakuen” where he acts as a teacher! Now, the “non-standard” teacher life by the strongest wizard opens!

(Source: MangaUpdates)

"Ecchi stuff that also may have a story...."

The Demon King led his army of demons to wipe out the human race. The Hero, Kail, and his allies attacked the Demon King's castle to defeat the Demon King. The Demon King is slain, but at what cost? Kail lost all of his allies throughout the war. Friends, family, lovers, comrades. All dead, and he is dying.
As Kail's life ebbs away in the Demon King's chamber, he notices a strange gem that the Demon King had coveted and approaches this relic to grab it; after an intense light glows, he is sent years into the past. After recovering from the initial shock, now in his younger body, he decides to avoid making the same mistakes of his first time through these years and to become stronger.