Grants access to the subquest "The Rage of a Queen". In this quest, players will be able to take on "Femme Cleopatra," and even recruit her should they prove victorious.

*After progressing to a certain point in the game, talk to the Bethel researcher in the Tokyo Diet Building to begin the subquest. Once completed, you will have the option of fighting Cleopatra as many times as you want.
*It is recommended that this subquest be attempted near the end of the game.

More details on the official game page of The Rage of a Queen ...