My Santa! (2005)

Original title: いつだってＭｙサンタ！

In the story, a girl called Mai appears before a boy who happens to hate Christmas. As it turns out he was born on December 24 and thus was named Santa, causing him to hate the holiday. Moreover, as a child, he never had any festive occasions, such as birthday parties. With the power of Christmas, Mai is given the mission to improve his luck and change his views for the better.