I'm searching for a manga set in a fantasy world, I can't remember if its a reincarnation manga, but the sister of the MC "who isn't his sister" is about to be forced to marry the local lord and the MC goes the the king so that he can do something about it. He gains some sorta "teacher" in his head or soul I don't know and becomes OP very quick. He goes to the King but finds out the princess is sick or poison and he makes a request that if he cures her he would make him the local lord or something I can't remember.

Almadianos Eiyuuden