This is really not mechanical ascension - Chapter 888 - 459: Invitation

Rhett never expected becoming king until he slayed an ice dragon out of self defense and fulfils an ancient dragon slayers prophecy which makes them to crown him as their king.Transported to a gloomy and medieval like world, he is faced with leading the dragon slayers, the weakest of slayers among other slayers - demon slayers, gargoyle slayers, ghost slayers and shadow slayers.But ruling isn't so glamorous as he had anticipated and he is instead a warrior, with a system like ability which he must level up by slaying Dragons.And to his disadvantage, the world he is his controlled by SLAYERIOUS, an unknown and unseen entity. But that won't stop Rhett, he intends on dominating his world and even daring to slay the strongest dragon still alive, ruieen.And who knows, he might just defeat SLAYERIOUS if he tries harder.[WSA 2025 ENTRY]

Introduction to One Piece’s Bounty System: Tianlei crossed the One Piece World and become the nephew of the Navy Admiral ‘Sakazuki, ‘Akainu’, Tian Lei thought it was very outrageous until he found himself having a [bounty system] that can be exchanged for everything in the world of One Piece. As long as you kill or capture pirates, you can draw a Skills, weapons, and devil fruits. Such as ‘Navy Six-style’ ‘Overlord color Haki (Busoshoku Haki)’ ‘sense color Haki (Kenbunshoku Haki) ”armed color Haki’ ‘devil fruit’ ‘sword skills’ have everything!

- Description from Novelupdates

This is the story of a young man who was reincarnated as a dragon with a near-insatiable curiosity. Initially sparked by questioning his own reincarnation, he quickly gets lost in the endless world of magic, using his deep understanding of advanced sciences to learn the laws and properties of a new type of energy known as mana.However, soon enough, the table would flip, and he would begin using that very same energy to expand his knowledge of science, to the point that he would begin questioning his own understanding of the world.Although not his original intention, with the combination of his intelligence, expanding curiosity, and the 'miracles' that occurred to allow for his existence, he quickly found himself climbing the mountain of strength as if it were a small hill before eventually climbing to a point where it seemed as if he himself was the peak itself.Even if.. that was never the case...There is mild gore, and profanity is 'censored' toward the beginning, but not later in the story.

“The war is finally over?! Then, what am I going to do with my life?” Caedrel, a man who had spent his entire life fighting, had no idea what to do next. Fortunately, he was offered to become a teacher in the greatest academy in the world. However, he wouldn’t be a normal teacher but a spy for his country’s Emperor! Doesn’t sound too bad, right? Well, it would have been great, that is…until he learned that his class was for the most talented(weird) students in the entire world.