Mage & Demon Queen

Maxima the elite mage signs up to slay the Demon Queen and emerge as the kingdom's champion. She arrives at the Demon Castle ready for battle, takes one look at Velverozah, and forgets the assignment entirely. Now she is determined to woo the queen instead, the two are stuck in an awkward courtship across enemy lines, and Velverozah's demon retainers are not pleased about any of it. Color webtoon comedy by Color_LES, ongoing since 2018, longest-running yuri webtoon on the internet.