With Zero Believers nearing the end, this series could be a great replacement.
It's written by the same author, set in the same world and time period as Zero Believers, and the main characters have the same traits and dynamics as the characters of Zero Believers, so fans of that series will likely enjoy this one as well. There's also a lot more background information about the world and about Rosalie's history that may also be of interest.
But there are also enough differences to make it new and interesting (e.g. it's set in an academy with a focus on dungeon diving and the MC is a swordsman).
The setting is on a different continent and with new characters, so it's not necessary to have read Zero Believers first.
VOL 1 description: (google translate)
He has the ultimate swordsmanship and the power of the Demon King in his hands.
Despite being from a distinguished family of swordsmen, Eugene has been branded a "defective swordsman" with extraordinary defensive power but no offensive power.
He leaves his country and enrolls in the Magic Academy, the highest educational institution on the continent.
At the academy, Eugene is asked to travel to the innermost part of the sealed prison, where mythical creatures lurk, as he is the only talented person who can withstand the miasma of the sealed prison.
Sealed in the innermost part of the prison, where even the most experienced wizards are forced to their knees, is Erinyes, the legendary Demon King who once ruled the continent.
Eugene, who has easily reached her, seems to be the only one who can make a contract with the Demon King...!?
A fantasy set in another world where a failed swordsman who seizes the power of the Demon King becomes the strongest sword saint!
