Strongest Sage With The Weakest Crest (Manga) Vol 03

Life at the Second Royal Academy starts off with a bang for erstwhile sage Matthias. When a demon infiltrates the school, it's Matthias who takes him out using his shiny new magical crest. But while Matthias might have won this battle, he's also just started a war! Thanks to Matthias's victory, the demon realm begins preparations for invading the human world! Will Matthias and his true power be ready and waiting for them? Square Enix Manga
(W) Shinkoshoto (A) Kansho & Hyoko, Huuka Kazabana