MTL - Plane Source Code - ~ Extreme exchange

Leon, a man who tragically died of exhaustion due to his sister's otome game, unexpectedly finds himself reincarnated as a young aristocrat named Leon Bartfort. However, he soon realizes that he is not alone in this body. Another mysterious entity already resides there, its voice echoing in his mind.Who is this second consciousness? Is it a friend, an enemy, or something far more sinister? Will they be able to come to an agreement to share control over the body, or will a fierce struggle for dominance ensue? Or perhaps their interactions will lead to unforeseen consequences?Intrigued? Then start reading!

The hero who was killed by the demon king ended up reincarnated as the son of the one who killed him! Thus began the life of the hero who donned in the mask of the ideal demon prince to topple his own kingdom while doing his best to prevent anyone from discovering his identity―― But to do that and blend into the demon tribe society, he had to kill his former comrades. Nevertheless, to become stronger, to save humanity, he had to walk through all kinds of paths of carnage! This is the tale of the demon race’s fake prince destroying his own kingdom.

O Hero, Trample Those Who You Should Protect!

TN: Most part of the other character in the novel is depicted from a non-human perspective so expect something that is completely different from the common sense of human.

My talent can be said above average but for my family I am useless. Six years after the incident that I caused I accidentally created a system.Now I wonder if I will fail again....with my new power I will make sure my cute little older brother, sister and especially my Father will pay the price of creating a monster.... Me

Sally, in order to fulfill her original wish, entered Beast World and transformed into a little white mouse, also binding herself to the Offspring System.[The Dragon Lineage has gone ten thousand years without new blood.][How many points for the Dragon Lineage?][Five hundred million!]