Additional content that will grant access to the subquest "Holy Will and Profane Dissent".
In this quest, players will be able to take on "Dagda", 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.
*It is recommended that this subquest be attempted at the end of the game.

More details on the official game page of Demon Subquest - Holy Will and Profane Dissent ...