As a boy, Argentum was a poison tester for a royal family. Later, he developed an immunity to toxic substances and became a master chemist with the ability to cure any illness. Returning after a long absence, he is assigned to be Princess Primula's bodyguard. But any potential relationship will have its limits, as Argentum's very touch has itself become poisonous.

The first eight volumes of Apothecarius Argentum were published in English by CMX from May 2, 2007 to November 3, 2009.