元弟子が魔王になったせいで、勇者に連行されました。

One day, Shidan — a traveling, struggling painter — suddenly finds himself surrounded by the Royal Knights, accused of being a great criminal. The charge? That he once trained and taught every form of martial art to the Demon King now ravaging the land. Shidan, who doesn’t seem like a fighter at all, is bewildered by the accusation. But when the knights, underestimating him, move in to arrest him— he unleashes an overwhelming power that leaves everyone stunned…!? A mysterious painter with hidden strength, a past shrouded in secrets— thus begins the tale of a man whose brush and fists may both shape the fate of the world!