In 'the innkeepers ghost story', the innkeeper is a central figure. They are likely to be the protagonist who has to face the situation with the ghost. The ghost is a major character too, as it is what makes the story a ghost story. Additionally, there may be other characters like the innkeeper's family or employees. If the innkeeper has a family, they might be affected by the events surrounding the ghost. The employees could also be involved, for example, they might be the first to notice something strange in the inn that is related to the ghost.
Well, clearly the innkeeper is one of the main characters since it's in the title. And then there must be the ghost. There might also be guests at the inn who could be involved in some way, like they might witness some of the spooky things related to the ghost or interact with the innkeeper during the ghostly happenings.