A oneshot from the manga, Seimei-Onmyouji Retsuden.
It's a story about a seimei and his aspiring apprentice, a young fox youkai.
(from B-U)

From the creator of tactics comes an exciting new story filled with beautiful girls & boys, black magic, and enchanted spirits that will appeal to fans of Rozen Maiden! Aspiring teen dollmaker Kashiwagi Kotoko runs into her favorite doll designer, Fool, only to be cursed with a shinshoku kiss. Now Kashiwagi has to make dolls for her or else Fool will turn her into an old lady! [From Justmanga.com]