A fantasy story about Kiska, a boy who is mistreated by the villagers. He manages to survive thanks to his childhood friend Namia, who was the only one by his side. One day, Namia is murdered by three men, and Kiska is accused of the crime and banished to an inescapable class S dungeon. However, he finds himself in a different world where he can use "Save and Reset" to get back on his feet no matter how many times he dies. The story is about Kiska's quest for revenge against those who wronged him and his friend

Local bullies tormented Kotaro when he was a youngster.
They were the skilled wrestler Akari.
Kanae, a basketball prodigy, and Shigure, a prodigy in video games.

Every day, Kotaro competed against these three guys in their respective sports with the intention of winning. Unfortunately, he was no match for them.

As a senior in high school, Kotaro now has another opportunity to confront them and exact his retribution...!

But he will discover a secret that he never would have expected....

Among the class transported to another world, Nagumo Hajime is an ordinary male student who didn't have ambition nor aspiration in life, and thus called "Incompetent" by his classmates.

The class was summoned to become heroes and save a country from destruction. Students of the class were blessed with cheat specifications and cool job class, however, it was not the case with Hajime, with his profession as a "Synergist," and his very mediocre stats.

"Synergist," to put it in another word, was just artisan class. Being the weakest, he then falls to the depth of the abyss when he and his classmates were exploring a dungeon. What did he find in the depth of the abyss, and can he survive?

The protagonist who was rarely ever at school during his middle school and high school days, is unemployed even as an adult. From morning till night, it was video games. For him who was ranked first worldwide, it was his life.

One day, his character is suddenly hacked. The data was unrecoverable and there was nothing that could be done. Feeling great despair at having lost his rank that he had bet everything to achieve in a world that controlled his life, the protagonist attempts suicide.

When he awakens, he finds himself inside the video game, no, it was a real world that resembled it. There, he notices that he has reincarnated into the the body of a sub character that he had created and bought premium benefits for long ago but had left neglected.

A reincarnated boy, Allen, gets granted by a goddess the cheat skill, "Restoration." Even though he can heal all and any injuries and illnesses, there aren't a lot of places where he can use that skill to the fullest, so he planned to "regenerate" the slaves he bought and lead a slow-paced life. But the healed slaves' cheats turned out so out of the ordinary that the crops they tend to and their living conditions turned for the better in a blink of an eye. The protagonist, Allen, who slowly but surely is robbed of opportunities to shine, tried to counter that with his modern knowledge, and yet, those talented slaves absorbed it all and brought success to any and all businesses. The protagonist is becoming irrelevant with each passing day?!

Da-in, ended up possessing the villain of a story.

To make Stardust — the story's protagonist and his favorite character in a dystopian manga — happy, he resolves to become the villain Egoistic for her growth.

Da-in deliberately causes terror to enhance Stardust's abilities and preemptively prevents all the tragic events from the original story, but in the process, he gains public support while also drawing Stardust's suspicion.

Stardust, who initially opposed him, gradually opens her heart, and soon even begins to show signs of obsession towards him...?

Takagi Kaito, a low status high schooler, your typical Mob character so to say, was just a normal everyday explorer who hunted slimes every day in the dungeons that appeared in Japan, earning pocket money while admiring his childhood friend, the class queen, from afar. One day, a golden slime he had never seen appears before him. After he defeats it, he obtains an extremely rare item worth hundreds of millions as a drop, a servant card that can summon mythical beings!! After he makes up his mind and summons it, a warrior maiden with unparalleled beauty appears. Rise above being just a mob explorer Kaito! A modern battle fantasy story has begun!

Noa Zuiho, a second-year high schooler with amazing tactical analysis skill, is brought to another world!

In order to save this other world from monsters, the goddess gives him the Power of Wisdom, which increases his tactical insight through... erotic actions?!

In an epic war between humanity and monsters, who will prevail? A brilliant strategist rises — with unorthodox methods and adult incentives to motivate his all-female army!

Just like how everyone adored heroes in their childhood, a certain young man adored those powers hidden in shadows. After hiding his strength and living the mediocre life of a mob character by day while undergoing frenzied training by night, he finally reincarnates into a different world and gains ultimate power. The young man who is only playing at being a power in the shadows, his misunderstanding subordinates, and a giant organization in the shadows that gets trampled….. This is the story of a young boy who had adored powers in shadows possibly eventually reigning over the world of shadows in another world.

The protagonist along with his step-mother, and 2 step-sisters are summoned into another world where demi-humans are the rulers as saviors, but its not to fight against a demon lord, its to fight an Undead Apocalypse monsters called "Dead Mell" that have overrun the world and that can only be killed by using weapons made with holy silver.

For that, a familia is made (group of 4 people) with them being the swordmaster that uses the holy sword, the guardian that uses the power of earth to protect, the healer that use the power of water to heal and the black mage that uses the power of fire to destroy.
The role of the guardian, the mage and the healer is to support the swordmaster that can only kill the monsters.

But to use magic powers one must offer part of your being as a sacrifice to form a contract with spirits, and the higher the sacrifice, the higher the power. Now they must choose who are the 3 that need to sacrifice part of their bodies to gain power and who will wield the holy sword.

A 34-years-old NEET otaku is chased out from his house by his family. Unattractive and penniless, he finds that he has reached a dead end in life and realizes that his life actually could have been much better if he had made better choices in the past.

Just when he was at the point of regret, he saw a truck moving at a fast speed straight towards three high schoolers in its path. Mustering all the strength he had, he tried to save them and ended up getting run over by the truck, quickly ending his life.

The next time he opened his eyes, he was already reincarnated into a world of sword and magic as Rudeus Greyrat. Born to a new world, a new life, Rudeus decided that, "This time, I'll really live my life to the fullest with no regret!" Thus, starts the journey of a man yearning to restart his life.

Lucas has a hard life. In his mid-thirties, a mixture of failures has left him old and crippled, playing pack mule to a couple of young adventures.

Then one day, he pulls a magic sword from a stone that tells him he has been chosen to become a hero. Given a youthful form, Lucas must use the power of the sword to vanquish evil and attain a massive harem.

Before you ask, it’s not isekai because he’s been in this world from day one. It is wish fulfillment, though, so in the end it’s basically the same thing.

Meet the Evil King Valt, ruler of the Continent of Darkness. After being defeated by a group of heroes, he was reborn as a human, with his powers intact!

"I'll start over in this world. And this time the whole world will be mine!"

Valt garners the attention of the elite adventurer Iris. With Iris as his guardian, he enrolls at the Royal Adventurer Training School and immediately surpasses his seniors with his abnormal power! In an unprecedented move, this maverick is designated "level 0." He goes on to employ his talents as an Evil King to great effect, dominating the new world he finds himself in...

From LHtranslation :

In a certain world, there was someone who excelled in magic combat, people called him 『Sage』. Seeking the strongest combat art, he devoted himself to research every magic and combat arts in existence. And the conclusion he arrived at was very cruel, 『My body is not fit for magic combat』. Yet he didn’t give up. He sealed his own soul with a magic art, and was reborn in a far-off future. And the magic theory in the completely changed world he saw there was of unbelievably low level.

A boy named Atsumu was branded as "useless" by his famous sisters and banished from his entertainment-industry family. However, hidden within him was an extraordinarily talented "behind-the-scenes support" skill that neither he nor his family had noticed! After transferring schools, Atsumu is now determined to live a normal life, but as he crosses paths with talented entertainers—VTubers, idols, and models—his natural ability starts to shine, making him their indispensable support. They can't help but adore him, turning his simple wish for normality into a showbiz underdog success story!

Standing at the crossroads of life; the important choices - “Flags”. Hatate Souta, a young man who can see these flags, transferred to “Hatagaya Academy”, a prestigious school in the metropolitan area. Not only does he meet beautiful girls in his busy school life, he even goes as far as living with them under the same roof! Surrounded by these flags, this enviable romantic comedy begins!

From MangaHelpers:
29-year-old programmer Suzuki Ichirou finds himself transported into a fantasy RPG. Within the game, he's a 15-year-old named Satou. At first he thinks he's dreaming, but his experiences seem very real. Due to his use of a 3-time-use special power (meteor shower), he ends up wiping out an army of lizardmen and becoming very high level. He hides his level and plans to live peacefully and meet new people, though developments in the game story (like the return of a demon king) might get in his way.

“O, Hero!” With that cliched line, Kazuya Souma found himself summoned to another world and his adventure-- did not begin. After he presents his plan to strengthen the country economically and militarily, the king cedes the throne to him and Souma finds himself saddled with ruling the entire nation! What’s more, he’s betrothed to the king’s daughter now?! In order to get the country back on its feet, Souma calls the wise, the talented, and the gifted to his side.Five people gather before the newly crowned Souma. Just what are the many talents and abilities they possess… What path will his outlook as a realist take Souma and the people of his country down? A revolutionary transferred-to-another-world administrative fantasy series starts here!

Takuya Seo is an otaku who likes "anime for girls" and can't say he likes it out loud. One day, he hooks up with two gals from his class, Amane and Ijichi, but it seems that Amane is also an otaku... It's about a school romantic comedy where the otaku meets the gals he like!

This is the story of a young slave gladiator in an underground arena. He doesn’t know about his past or how he got to where he is, only that his name is Aegir, and that he is strong.

One day he kills the boss and escapes the arena, joining a band of mercenaries as a new recruit. During one mission, they encounter the vampire, Lucy, who slaughters the band with her inhuman strength. After learning that Aegir only knows how to kill, Lucy lets him stay at her house, educating and taking care of him.

Two years pass, and on the day of Aegir’s departure, they both exchange a promise that if Aegir becomes a king and owns the land of Erg forest, he can come and take her as his woman. Making this his life goal, Aegir set out on a journey to become a hero, a king, and found his own kingdom.