Monster no Niku wo Kutteitara Oui ni Tsuita Ken

モンスターの肉を食っていたら王位に就いた件

Eat Or Die! The first prince of the kingdom of Farune, Mars, is only twelve years old, yet he lives in fear of assassination. In order to avoid the deadly poison in nearly all of his meals, he slips out of the castle into the nearby monster-infested forest, where, battling monsters and his own hunger, he has to hunt for his meals in order to stave off starvation. Then, one night, as he’s searching for his next bite of monster meat, a red-haired woman shouldering a greatsword appears before him and says to him, “You have promise. Become my apprentice.” How is he supposed to tell her that this must be some sort of mistake? But there’s a secret that only she knows, and that he’s stumbled upo…