How Not to Summon a Demon Lord (Manga) Vol. 19 (manga)

With the Demon Overlord Modinaram threatening all humanity, Diablo decides it's time to raise his level as a fighter, ASAP. After a quick trip to Faltra City to gather information, he sets out for the northern mountains of the Demon Lord's Domain. His plan is to find the swordmaster Graham, study under him, and learn his peerless swordsmanship.

Instead, he winds up discovering a cute dwarf girl named Sasara took over the mantle of Swordmaster just half a year earlier! It seems like becoming her disciple won't be easy, either...