Rinji Aen Rinjian

Lindsay is a top-secret spy about to take on her most difficult mission yet: to disguise herself as a man?! Her target is the Duke. Rich, mysterious, and… an infamous womanizer. Cutting her hair, drinking elixirs to hide her voice, as a servant she must infiltrate his manor and investigate the mysterious disappearance of lords and ladies in the area. However, when she meets the Duke for the first time and he kisses her, is it her identity that's compromised or her heart…

(Source: Tapas)