I am trying to find the Manga or Manhwa with this Description

[NotANazi]

Looking for a Manga/Manhwa where the MC is like reincarnated into a novel and he has a sister whom is a maid or something of a prince. He is a warrior of the clan and is recognized by like one of the elders and has to save a princess who is suffering from a sickness which makes you stronger and he went through the same thing. I am also fairly certain he helps save the a Female Character during like a festival of some kind when the demons attack it. Also the people he descended from betrayed the clan or something and he and his sister are like the last two left I think.
Pretty Please help me I remember it so vividly but, I just can't recall the name of the story or character.