Hershey (ハーシー Hāshī?) (Viz Media: Cocoa) was Erica's dog when she was a young girl on Mars. It was first mentioned by Erica to Yoko when they were crossing a minefield together under threat of death by a squad commanded by Maltan, but did not appear until Mars Chronicle.
It is later revealed in a flashback triggered by a return to her former home in Curie Stadt that the dark history behind Erica's family was revealed. Her parents were abusive towards her and her father employed Hershey as a guard dog. At one point he goaded Hershey into tearing off Erica's left forearm while laughing as he had a drink. Hershey was subsequently poisoned by a pair of unnamed men who coveted Johan's treasure who Erica led back to her home to get revenge on her family.