Ginga Nagareboshi Gin
Around 100 years ago, Black Wolf's pack in Hokkaido had fights with Gaou's pack about territory and prey. When humans came and threatened his pack, he went to Gaou's Underworld kingdom to ask for help. Despite their earlier enmity, Gaou let them in since he understood how bad situation they were in and felt sorry for them.
However, Black Wolf was evil and his kin plotted to take over the Underworld for generations. Purple Wolf, his ninth-generation descendant, succeeded in this.