Strongest Sage With The Weakest Crest (Manga) Vol 13

Once the world's most powerful sage, reborn Matthias has gained the optimal crest for magical combat many thousands of years in the future. But with magical knowledge at an all-time low in this new era, no one recognizes Matthias's crest for what it is. It turns out that the demon tribe is responsible for spreading misinformation about crests and causing an overall decline in humanity's magic capabilities, leading to Matthias's battle against the demons who seek to destroy humanity! Square Enix Manga
(W) Shinkoshoto (A) Kansho & Hyoko, Huuka Kazabana