A Hentai System in the World of Danmachi - Chapter 84 - 83 - Goddess Ishtar.

Lee Jin Woo once lived a dismal life.
He lived pitifully on a day to day basis in his five-pyeon studio filled with mold.

Then, one day, he died in a sudden fire.

When he wakes up, he finds himself inside a novel.
But there’s just one issue…
He had become the novel’s villain!

It was a life without regret. My parents were in good health, and I wasn’t homey enough for me to combine my studies and part-time jobs.

Bizarre clouds billowed by in the sky, as if in a hurry.

During an anti-drug operation in the city of Gongzhou three years ago, a chain explosion had gone off on site due to a mis-judgement made by the Commander-in-Chief Jiang Ting, and caused the anti-drug detachment team to suffer great casualties as a result. Three years now, Jiang Ting, who was supposed to have already been killed in the line of duty with not even a body left to bury—miraculously woke up from a coma.

His heroic soul had never been at peace. He returned from Hell back to the living, to give everything he had to bring the bloody and bizarre truth back to light.

- Description from Novelupdates

Guy Larks was famous in his original world for his widespread charity work in poverty-stricken and war-torn nations.

He was especially known for his efforts in developing schools and educational facilities for children, as well as teaching and nurturing many students.

So it was devastating news to learn that he wouldn't live past his 30th year.

But he was given a second chance! A new life in another world, as a down-by-the-dumps teaching apprentice in a world of magic and wonder. He was given no cheat, just a Repository of Knowledge holding all the information he could bring with him from his previous life.

In this new world, Guy rediscovered his life's true calling! Ride along on Guy's journey as he changes the world one budding mind at a time, as the greatest teacher this world has ever seen!