Tensai Kyuuteigaka no Yuuutsu: Do-S na Juusha ni "Dansou" ga Barete Odosareteimasu

The "genius boy artist" who's the talk of the town is actually a girl named Gisele! But then Logan, a mean-spirited attendant of the chancellor, discovers her true identity! Threatened into doing whatever he says so that he'll keep quiet, Gisele has her masterful painting skill put to use by helping to look for the person who caused a suspicious death in the royal palace. Worse yet, he begins touching her and treating her like she's his girlfriend... even though he knows she just wants to be treated like a "man". This attendant is a complete sadist!

(Source: B's-Log Bunko, translated)