Cassandra Cain (Batgirl), Noriko Iwakari (Repeater), Julia Jacoby (Exalted versus World of Darkness), and Erza Scarlet (Fairy Tail) go to the Danmachi universe, plus a guy you don't care about but gets to dick them all. (Content Note: There is no NTR in this story. One of the characters in the story has virtually no verbal filter and a wide variety of fetishes, so she mentions NTR at various points, but she will never have sex with a man other than the protagonist.)