The First King of Beasts - Chapter 30 Quest End

Among the demons, the supreme ones are called “Great Saints.”

A young man leaves his mountain village and travels around the world. By unceasing efforts, he finally becomes a legend of the age.

- Description from Novelupdates

An ordinary (?) grandfather, Choi Chuntaek. In an effort to protect his granddaughter, he started the virtual reality game 'Arkstar.'

Then... he accidentally obtained a legendary class?

The World of Ephesus. A vast world plagued by Breaches containing countless Beasts of Corruption. A World on the brink of ruin as the Four Human Lineages defend the last bastions of Humanity! With the power of Gem Masters standing against the Beasts of Corruption, the flames of Humanity seek to burn ever brighter. In such a world, in the Mortal Branch of the Asmodeus Bloodline, Alexander awakens a Gem Socket that others consider defective. A Variant Gem Socket. Looked down upon by those who do not understand it, this supposed defect may just be the solution that the burning embers of humanity were waiting for. Follow Alexander as he entirely warps the perception of what a Gem Master is- as he embarks on a journey to become...The Empyreal Gem Master!

Yan Sagawa is the top academic master in the world of Conan, known as a national treasure talent.

No one knows that he is actually a time traveler, carrying the most powerful Xueba system.

But he also has troubles recently, and he has awakened a second system — the Great Onmyoji system.

Whether to believe in science and become the father of all mankind or believe in theology to become the god who controls reincarnation, this is a question

. . .

After thinking for a long time, he decided that he wanted them all!

Conan: This is impossible murder! Is there really a ghost?

Sagawa Yan looked at the shikigami flying in the sky and smiled without saying a word.

Kidd: What kind of magic is this, how could you hide it from my eyes.

Sagawa said: This is science, you scumbag

- Description from novelbuddy