紅蓮の魔女と不死の魔王

From Author Wars - https://authorwars.com/books/hong-lian-nomo-nu-tobu-si-nomo-wang-3137868.html

Overview:

Title: 紅蓮の魔女と不死の魔王
Author: 大崎アイル
Year: 2020
Type: Novels
Series: 信者ゼロの女神サマと始める異世界攻略 / Full Clearing Another World Under a Goddess with Zero Believers
Number in Series: 6

Variant Titles:

2023. The Crimson Witch and the Undead King