Chouetsu Kyuu Seikenshi, Makenshika no Sue Musuko ni Kaiki suru

In a world where humanity has been pushed to the brink of extinction by “Invaders,” Zenon Glorious, a 9‑Star‑class Holy Swordsman, fights to the bitter end. In exchange for the lives of his comrades, he is sent back into the past. When he opens his eyes, he is no longer in his familiar body. Instead, he finds himself in the body of Noah, the youngest son of the prestigious Daskul family—looked down on as a hopeless failure. To defeat the Invaders that once devastated the world, Noah rises up, armed with his knowledge from his previous life and a one‑of‑a‑kind power: “Magic‑Holy Core,” a fusion of a magic core and a holy core—two things that should never be able to coexist. https://ebookjapan.yahoo.co.jp/books/972263/