One Piece: The Navy's Eight-Year-Old Technology Maniac, the Four Emperors Are Crazy

After traveling through time, Xia Yu became an eight-year-old kid, awakened his technological system, and used his brother Kizaru's identity to join the Navy's Science and Technology Department.
Create Seraph at the beginning, upgrade to Admiral Seraph, and Rocks Seraph!
It destroyed the three major balancing forces of the sea, the navy, and overwhelmed the Seven Warlords of the Sea and the Four Emperors!
There is also the Cosmic Fruit Tree, which is superior to the Devil Fruit Tree. The power of the fruit on the tree includes all the world's powers!
Iron Man mecha, domineering apple, kinetic energy drink, nuclear peace activist...
All kinds of black technology are available!
From then on, the entire pirate world went astray...
Blackbeard: Maybe you don’t know, but my pirate group was wiped out by two of the lowest-level Seraphim!
Doflamingo: A new era has arrived, but it is an era that belongs to Xia Yu alone!
If you want to defeat the navy, you can only rely on technology!
After the pirates successfully replicated some of Xia Yu's technological products, a competition for technological research and development funds between the navy and the pirates officially began.
Four Emperors: In order to resist the navy and replicate Xia Yu's technology, we spent all our savings!!!
Navy: Do you think we can get any better?
Speaking of which, you may not believe it!
The Celestial Dragons have no money!!!
Xia Yu: It was you who gave me money and begged me to do the research and development.
No money, is it my fault?