Heart-kun has a perfectly heart-shaped spot on his side, shown in the topmost pair of photos of Heart-kun as pup (left), and as a grown dog with his nephew Love-kun (right) who has a slightly less perfect heart on his fur.

The middle photo is the nephew's mother from the same lineage nursing the litter that produced the second heart pup. In 2009 two-year-old Heart-kun sired a son, Kokoro-chan, who also bore the heart marking.

These belong to a woman who owns a pet shop called Pucchin's Dogs in Odate, Akita, Japan. They have become celebrity pets throughout Japan with people dropping by to pet them hoping the good luck will rub off on them.

They are the subject of a dvd documentary, picture books, and the owner has turned down huge amounts of money for them.