Seikenshi-sama no Maken-chan

Kale is a newly promoted paladin tasked with protecting the kingdom. During the ceremony to select his holy sword, he instead awakens a demon sword capable of taking human form. This type of weapon is regarded as dangerous due to its immense strength. The demon sword appears as a young woman named Reece, who gazes at Kale with admiration and addresses him as master. Struck by her appearance and demeanor, Kale finds her extremely appealing and resolves to ensure her happiness while managing her power. Unforeseen challenges soon arise from this decision.