Itsudatte My Santa! is a manga by Ken Akamatsu. It is a one-chapter manga and was written between Akamatsu’s A.I. Love You and Love Hina. An anime OVA of two episodes was released on December of 2005 in Japan.
Summary of the manga Itsudatte My Santa:
It’s christmas eve and Santa is pretty sad because he is alone. You read it well, this guy’s name is Santa, his birthday is on 24th of december and his parents went on wedding anniversary holidays as they do every year.
Maï, a middle-schooler, decides to spend the night out with him. She soon unveils that she is the real Santa Claus, but Santa doesn’t believe in the magic of christmas anymore (you can feel the irony).