MY BLASTED REINCARNATED LIFE

When the warrior Hamel sacrifices himself to protect his rival Bermut Lionhart, he makes Bermut vow to vanquish the last of the demon kings. Reincarnated with his memories 300 years later, he is shocked to find that not only are the demon kings still alive, but that he has been reborn as Eugene Lionhart, a member of his former rival’s bloodline! Now, as Eugene comes of age, he must train to prove himself as a Lionhart and eliminate the remaining demon kings once and for all. (Source: Tapas) — Description from AniList community (anilist.co).