It is common knowledge that it is best to become an adventurer when you are as young as possible. It is common knowledge that it is best to become an adventurer when you are as young as possible, because the magical power that is the basis of an adventurer's strength will hardly grow if you don't train it while you are young. But this man, Rick Gladiator, who became an adventurer when he was over thirty years old, had the combat power of an S-rank adventurer, the highest rank in the world. In fact, Rick has lived an unimaginable life with the members of the legendary Orihalcon Fist, a party of the continent's strongest adventurers. From dragons to vampires, Rick's fighting prowess, trained by his literally "monster" mentors, allows him to defeat elite adventurers one after another who try to underestimate him.

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Jirou, a third-year in high school, is forced to live with a gyaru named Akari under a course called the "Couple Practical". In order to be paired with their own romantic interests, they're going to act as a married couple...!?

From Operation Boredom:
It is currently the Taiheimeji Era. It is a reign ruled by the Tokugawa shogunate. Inside this shogunate, there is a group of warriors that support the government. They are the Manyuu Clan. In this current era, breasts mean everything. If you have breasts, you are guaranteed wealth and popularity. If you lack them, you are rarely considered "human". Members of the Manyuu Clan help raise the future big breasts. Written on a secret scroll possessed by the clan, there is said to be various techniques on how to grow big and beautiful breasts. Chifusa is to be successor of the clan. However, she takes the secret scroll and runs away with it, hoping to fight against the cruel world that the Manyuu Clan has created.

I entered the world of a novel suddenly. I thought that I could return to reality by falling in love, but death was what awaited me in the end. Defenestration, strangulation, poisoning, drowning, and burning to death... Even after dying a hundred times and returning, the novel still doesn't end...

Karen Haier, who greets her 117th birthday trapped within a novel, now decides to become a murderer.

A story about a boy who doesn't want to see the girl who wants to see his boobs.
Artist’s Twitter: https://twitter.com/kantyo4545

For 52 years, Takumi Fujimura, a craftsman who has continued to hone his skills at a town factory, finds himself in a predicament when he has a dispute with a client and stops getting loans from banks. After many years of hard work, he finally collapses, but he awakens in a different world where he meets Frau, a girl who aspires to become a hero. With the benefit of modern technology and decades of crafting skill, can Takumi take this new world by storm?

Official Raw: https://www.pixiv.net/artworks/115806876

The Jester ― More commonly known as the ‘Playboy’ Dylan, was fired from the party of the Heroes. The self-centred Heroes didn’t understand Dylan’s importance to the group.
They were just a group of one-man teams. Not interested in cooperation at all. Any failures are blamed on the Jester. Dylan, who was disgusted with such companions and was sick of playing as their comedic foil, happily accepted being kicked out.
The Heroes didn’t know. After saving them many times over with his magic tricks, the level 99 Jester can change his job title to that of a ‘Great Sage’.
“Life, how about a rewrite?”
He’s done being the clown. From here on out, he’s going to take the leading role.

A hero should never kill anyone, not even the worst of villains. Gangyu could never understand why his team of heroes lived by those words, but he tried his best to do the same… until the villain who wiped out his squad killed his brother in prison. Gangyu breaks his vow and enters Ruculus with permission to kill as the prison’s executioner. Now, he must fight his way through the villains to kill the worst of them all.

I found myself possessed in a game I used to play occasionally.
And to top it off, I'm the female warrior of a barbarian tribe that only has bad endings.

...Alright, let's escape.

Late at night in the middle of my part time job at a convenience store, I had an encounter with a robber and was mercilessly stabbed to death.

As I was about to lose my consciousness, I thought about how much I wanted to do this and that when I heard a voice……

『The wish to be summoned has been confirmed. Granting Unique Skill 《Jack of all Trades, Master of None》』

Rude words such as that were said. Jack of All Trades, Master of None? Don’t screw with me!

Such thoughts and wishes were for naught as my consciousness faded, when I came too I was standing on a green foggy hill.

(no overpowered protagonist and no harem)
[Description from novelupdates.com]

From Udon Entertainment:
When Mara Shin’s dog Toto gets lost one fateful day, she follows his trail along some yellow brick road and ends up in the wonderful land of Oz! Everyone instantly starts calling her Dorothy, but these aren’t the cowardly lion, brainless scarecrow and heartless tin man adventures you remember. This fantastic fairy tale features familiar characters…but with a definite action/animated twist!

A classic redone for new fans. Met Mara Shin a ordinary student whose life was normal until one day she chase after her dog Toto. That when she saw the yellow brick leading her to Oz. There thing are not the same Oz that we know. Colons, Robots, and Chimeras oh my. So join Mara (Dorothy), Abbe (Scarecrow), Namu (Tin Woodsman), and Tail (Cowardly Lion) down this twist adventurer down the yellow brick road.

This is a story about the main character named Inuyama, who is on the edge of life with no job or savings. One day, he is tasked with the role of "broadcast advisor" and "pseudo-boyfriend" of a gravure idol. Can he reach the top of the world of gravure in this romantic comedy harem? ♡

After years of missed connections, our protagonist reunites with the junior he got along well with in high school. However, apparently, she has become a famous influencer.

Everyday is a normal day in the small town where Kasuga Arata lives. However, everything changed on the day of the Black Sun, and following it, a magician appears before him. The Black Sun caused the Breakdown Phenomenon which destroyed the town where he lives. Because of this, his normal life was artificially reconstructed by a Grimoire that his childhood friend had left. Just what is the purpose of the magician coming to the town? What will he do with the Grimoire's keepsake?

A teacher finds herself getting a marriage proposal from her former student, who has had a significant growth-spurt since they last met.

Energetic girl Kyou meets quiet girl Makoto, who only communicates using sign boards numbered 1 to 10. At first, these polar opposites interact rather one-sidedly, but gradually become able to understand each other's feelings.

Who will you “play” with tonight—? A sweet and sugary harem romantic comedy about sleeping with elves ♡

I eat the same things at the same time. Your protagonist Omi Sorasaki is a high school student who's a devotee to the ordinary. But one day, a mysterious and beautiful girl transfers over and says to him "I have something to say to you alone after school." But what happens after is only just the first wave of an assault on all that is ordinary!

Author's Twitter: https://twitter.com/naonoshime

Hotta Youta is killed while returning home from work on a cold evening. He wakes up being carried by a bunny-eared woman! Featuring Reincarnation, Guns and Harem, its a Gun vs Magic Story that gives Hotta Youta a new life... and an edge!