Is It Wrong to Try to Pick Up Girls in a Dungeon? On the Side: Sword Oratoria, Vol. 3 (light novel) — Fujino Omori

Aiz is stronger than ever, but she has never been more restless. The blackrobed "client" who lured Lulune Louie into a dangerous job is roping in the Sword Princess with a quest she can't refuse. She knows full well how wary she should be, considering this person's last job ended in an adventurer's brutal murder, monsters attacking Rivira, and Aiz's battle with a distressing monster tamer who confronted her with a name no stranger should know.

But when she is offered clues that could lead to revealing her new enemy's identity, Aiz launches herself headfirst into the Dungeon--alone. Loki Familia is quick to chase after their idol once they find out what she's up to, but nothing can prepare them for the incomprehensible dangers lying in wait for them.