Maou-sama wa Yuusha no Ken de Midaretai
魔王さまは勇者の剣で乱れたい · まおうさま わ ゆうしゃ の けん で みだれたい
est. Rough estimate based on volume count, reprints and magazine — not an official figure
External databases: MADB · AniList
How to compare editions, collected volumes and ISBNs / Sources, updates and corrections