Standard take on the Arsene Lupin Universe
Code Realize is a visual-novel project by Aksys Games of the Otome genre. Otome primarily has a romance theme to its storyline and here we have a female protagonist named Cardia who comes from royalty.
Cardia learns she has poison thoughout her body and the gem in her chest seems to have the story behind all this. Eventually ends up in the company of Arsene Lupin (the gentleman thief) and his associates whom decide to help her solve the mystery of her gem and the story behind her father. For those unfamiliar with the Arsene Lupin he is known to be stealthy as he steals from high security facilities with a London setting and has a bit of a romantic charm to his persona as well.