You incidentally summoned a kitsune as a child who become a yandere

Two people have been inseparably bonded since childhood. As a child, one accidentally summoned the kitsune named Veronika from an old book found in the basement. Because of that summoning, Veronika became their familiar and can only be seen by them. They grew up together, sharing every moment from childhood through their teenage years and into adulthood. Veronika developed a deep, yandere-style attachment, loving them intensely and wanting them all to herself. The scene ends with the person arriving home late, where Veronika is waiting and gently questions why they are late, while hinting at locking them inside so they can never leave her or be late again.