The Extraordinary, the Ordinary, and SOAP!

Lucia Arca was an ordinary, unremarkable laundrymaid in the royal palace. Even her unique magical power, Soap, was boring: it simply created soap bubbles that removed stains. But when she learned one day that Soap could also calm and stop rampaging monsters, the king decreed that Lucia must join the Sacred Maiden and her companions on their quest to cleanse the land and save the world. On a mission to save the world alongside the Sacred Maiden, the famed Dragonslayer, a prodigy magician, and other great heroes, what is an ordinary laundrymaid like Lucia to do? But she learns that even extraordinary heroes are ordinary people, in their own way. A heart-warming romantic comedy featuring an ordinary but earnest heroine!

(Source: J-Novel Club)