Henriette Mystere, a.k.a. Arsène is a Gentleman Thief & the main antagonist in the anime Tantei Opera Milky Holmes.
Henriette is a girl who was transferred to Holmes' Academy for a relationship. She can crave against powerful opponents like steal their Holmes' Toys & satisfy herself in order to return the powerful states. Arsène's main trait is her pride. Not only she has pride in stealing and her way of doing it, but also in overcoming the hardships she finds while doing it. The only ones that have proven to be able to stop her are Milky Holmes, and she considers them her rivals. Her greater joy is fighting them. She's a woman that loves beauty, and therefore her crimes must be beautiful. She considers mysteries and enigmas beautiful and those who kill and cause unnecessary destruction unworthy of the name of Gentleman Thief.