Sweet Rein

Sweet Rein (よろしく・マスター, Yoroshiku Masutā), known as Yoroshiku Master in Japan, is a shōjo manga by Sakura Tsukuba.

Plot
One day when 17-year-old Sagara Kurumi accidentally bumps into a guy on the streets, reins suddenly appear and binds them both! What is this?! Things get even more confusing when the boy, Kaito, clasps her hands and calls her his master! When Kaito transforms into a reindeer it just becomes too much for poor Kurumi who's out as a light. But it does indeed seem like Kurumi's a santa and Kaito's her reindeer and that they've got an important job to do on Christmas Eve~