I hate being in pain, so I think I'll make a full defense build - Chapter 351.1

What happens when a fanfic author with a habit of lying and scheming suddenly finds himself as a self insert during Duelist Kingdom? What happens when you have Yugi, Joey, Kaiba, and the rest encounter someone who knows all about every major player in their saga... and sees no problem with abusing said knowledge? Chaos, dear reader. Sweet, sweet chaos

Every human on Earth was transformed into a summoned monster and was summoned to another world.

However, he did not know that he was not raising just a harmless pet, but a biological weapon secretly made by the government… a real monster.

As a former librarian, Rand felt that he had been living an ordinary life, the one that he had reclaimed unconsciously every single day.

Recently, he has been a little upset because the pet fish he accidently brought home to raised seems to have undergo some strange changes

Well, it turned into a merman.

- Description from Novelupdates

This novel is also known as Endless Bloodstone / Infinite Bloodcore

In the dark night there is no light, save for the sound of war drums and rally cries. The young man listens carefully, it is his heartbeat and the flow of his own blood.

What hides in the darkness ahead? Is it man, god or… a monster?

There is no such thing as the best road. However, the journey beneath one’s feet is unbounded!

- Description from Novelupdates