What are the major differences? Is the plot different?
The base are the same he reincarnated to have his revenge anf Wrath ( the demon who disappeared of the manhwa) helps him. His family and team will becomes better do their mission etc there the basics...after some mission or important fight disappeared, Wrath who is always there disappeared too ( was happy he was there in the ln since he is a laughing thing later it's useful since there'll be lot of anguish).
Yua ( little girl in the castle), should have come with Rion to the Zhiegjart and live in Raon home, cause Eden will comes for her until she is protected ( they want to put the siren mask on her).
And there some others things but we'll there too much....
Ok there really a world difference between ln and this so except for the beginning and the name of characters we can't even say it's the same things, I won't continue to read it can't stop to compare both.....