How Not To Summon Demon Lord Light Novel Softcover Volume 07

With Diablo learning of a ritual passed down by the Dark Elves that may be able to remove the remnants of the Demon Lord's soul still slumbering within Rem's body, he tags along despite her insistence to solve her personal problems on her own. Out of concern of course; it has nothing to do with the Dark Elves having gigantic breasts according to the game! R-Right...?