In 'Pulp Fiction', Butch is a boxer and Captain Koons has a connection to Butch through Butch's father. Captain Koons was given something to hold onto for Butch. Their relationship is mainly centered around this odd transfer of an item that holds significance in Butch's family history.
In 'Pulp Fiction', the relationship between Butch and Captain Koons is an interesting one. Captain Koons has a role in Butch's life due to his relationship with Butch's father. He was entrusted with an item for Butch. Butch, on the other hand, has his own life as a boxer and his own set of problems. When they interact, it's this collision of two different worlds. Koons represents the past and this strange obligation, while Butch is more about the present and his own desires. Their relationship is a key part of the movie's convoluted and engaging narrative.