Aileen overcame all the difficulties and got engaged with Claude. Just when she thought she found her happily ever after, she receives news that a demon named Ashtarte attacked a human village in the Mirchetta region. Sensing new dangers, Aileen infiltrates Mische Academy in the Grand Duchy of Mirchetta to investigate the situation. There, she meets James Charles, the last boss of Regalia of Saints, Demons, and Maidens 2 as well as the other quirky members of the student council.
You're trying to solve a case about a vampire,
 but you're scared of the demon lord?
تحاول حلّ قضية عن مصاص دماء، لكنّك خائف من ملك الشياطين؟
Du stürzt dich mit Eifer
auf den Vampir-Vorfall,
¿Quieres resolver el caso de un vampiro
y te da miedo el Señor Oscuro?
¿Quieres resolver el caso de un vampiro
y te da miedo el Señor Oscuro?
Tu t’apprêtes à enquêter
sur une affaire de vampire,
Vuoi risolvere il caso del vampiro 
e hai paura del Re Demone?
Quer resolver um caso sobre um vampiro,
mas está com medo do lorde demônio?
Ты ведь дело о вампире 
раскрыть пытаешься,