The title is a play on words: the actual Kanji used are ai (穢, dirty) and yoku (翼, wing), rendering the primary meaning of `Eustia of the Tarnished Wings`. However, aiyoku is a homonym in Japanese, and also means `worldly passion` or `lust` (愛欲). Accordingly, the alternate reading is `Eustia of Passion`, which is an allusion to eve...