From A Stronghold NPC To The Final BOSS - Chapter 43

Reborn and returning, he possesses medical skills, can practice immortality, has a slave who is the king of killers, and a maid who is the school beauty pursued by everyone. Even casually taking out a piece of trash can shock the world. His return has set this world ablaze.

In one moment, he was walking down the street with his little sister—In the next, he had traveled to the world of One Piece, carrying a system that could extract, record, and fuse genes to cultivate powerful lifeforms.Thus began a leisurely and carefree life in the most chaotic world imaginable.When bored, he’d snatch a bit of heavenly tribute meant for the Celestial Dragons.When curious, he’d raise a few cute kittens and bunnies just for fun.When restless, he’d wander through the territories of the most fearsome powers in the New World.Life is beautiful—so why bother taking anything seriously?

The low-ranking behemoth, the iron mountain is invincible in the horizontal push, and it is called the king of the backing.

- Description from novelbuddy

This is the story of Ryo, who was reincarnated in the world of swords and magic.It is a story of the royal road to survive using the magic of water attribute.What is magic? What is swordsmanship?How does it relate to the laws of physics that we know?Or what is politics? What is a nation?Why are there many 『kingdoms』 in reincarnation stories? Will republics not work?Can it be written …?Since it is a water-based magician, so it shall start with 『Hydrogen bond』!