Koushaku-ke no Ryouriban-sama: 300-nen Ikiru Chiisana Ryourinin

Luciel, a boy whose father is the world's strongest "Sword Saint," is abandoned in the mountains because of his weak constitution. He is forced to survive alone in a mountain infested with magical beasts. However, he accidentally discovers that the magical beasts are edible, and even acquires skills from the food he eats...!? A gourmet x battle fantasy about a little boy chef!

(Source: Kodansha, translated)