This story takes place after the events of Dmc:5 Where Dante and Vergil head down into the depths of the underworld to finally cut down the Qliphoth tree and stop the underworld for taking over the world

as they are cutting down the tree they notice an odd looking crystal hanging from one of the Qliphoth branches when they go to investigate the find a person inside seemingly unconscious

Dante:”Who the hell is this…?”

Vergil:”This is…Curious”