Sisi is a dog that lives in Saint-Germain's mansion. He was rescued by Impey after losing his leg. Despite being given a new mechanical one and being cared for after injury, he didn't warm up to any of the people living there until Cardia arrived.
Sisi is a corgi with white and brown fur with a heart-shaped marking on his left hindquarters. His left front leg is a steam-powered prosthetic made by Impey. He wears a black top hat with a gold ribbon around it and a blue-and-gold striped bow tie.
Sisi is very particular about what people he shows affection to. Despite Impey being the one to save him and help him walk again, he is aggressive towards him, and he doesn't care for any of the other men, either, according to Lupin. However, upon first meeting both Cardia and Delly, he immediately starts behaving in a more friendly way.
- He was named after Empress Elisabeth of Austria by Impey.
- His name is sometimes spelled "Sissy" by fans, due to the Japanese official site's usage of that spelling.