Skeleton Knight, in Another World - Chapter 13Volume 5 -

“There are no heroes. In life, the monsters win.”

...

In 2106, [Mayhem Online], a fully immersive VRMMO game, was released. Soon, it dominated the world's economy when people could exchange the in-game currency with real-life currency and vice versa.

In the year 2107, Flynn Grey, a 22-year-old college dropout with an ambiguous history, joined in the fray of billions of people that had already started playing [Mayhem]. Hoping to uncover the game's secret and earn a fortune, he spent months on adventures without fruitful results.

For better or worse, Shura, Flynn's in-game character, ends up in a great Wyvern's den, acquiring a hidden class and a monstrous race. Join him as he defeats his past and paves his way into becoming a true legend in both worlds.

Perfect. That’s what people call Princess Elysia. Blessed with rare red fire magic and trained by the best, she’s the shining jewel of the kingdom of Arvandor. But perfection has a price. When the ruthless Demon Queen Malvoria sets her sights on Elysia, all hell breaks loose—literally.As Malvoria’s army lays waste to Arvandor, Elysia’s life is shattered. Her beloved father, the king, is slain, and her once-peaceful home becomes a battlefield. Forced to flee with her girlfriend, Zera—the fierce daughter of her magic teacher—and her mentor, Lady Seraphina, Elysia’s journey of survival begins.But Malvoria wants more than just a kingdom. She wants Elysia, and nothing will stand in her way. As Elysia’s hidden powers awaken, an unexpected and dangerous attraction sparks between her and the demon queen.

The world was once at war with 10 alternate worlds. This was known as the Concept War and our world won 60 years ago. All of this was concealed so no normal people are aware of this fact in the current time.

After the death of his grandfather, the high-school student Sayama Mikoto is suddenly summoned by the giant corporation IAI. He learns this world is headed for destruction due to the acceleration of the Minus Concepts. To prevent this, negotiations must be undertaken with the survivors of the other parallel worlds so their 10 concepts can be released.

And so Sayama is caught up in the final battle to clean up after the Concept War which left behind so much enmity.

The mountain village boy accidentally got the fairy gourd, and he rose step by step to cultivate immortality and longevity.

Ripe elixir, mortal flow.

- Description from novelbuddy