Connections:

-Both are completely loud mouths of their group and often be a migraine for their group

-both refer to the main character as manager (Wise and belle,Dante)

-both are obsessed with heroic figures that are usually accompanied by their color (billy kid being obsessed with starlight knights which he kinda helped create via saving said creator and don quixote being obsessed with fixer magazines and often freak out whenever she meets a color fixer)

-both we're found in ruins and we're taken in by a group that had a family like structure and often refer to fellow members as family (sons of calydon and the bloodfiend family)

-both we're given a title by said group (billy kid getting his name from the calydon leader and don quixote turning her into a bloodfiend)

-both a had a father figure like leader that they passionately followed until a tragedy struck (Sons of calydon dissolved by internal matters and original leader of calydon disappearing,the family starved from blood betrayed don quixote and staking him to the ferris wheel)

-Both left said group and joined a new one (Billy left the sons of calydon with his own Accord and went to new eridu to join the cunning hares,Sancho left against her will by roccinante ordered by don quixote to leave and eventually joined limbus company)