1. A computer-implemented personal service support method for assisting an inquiry about a user operation in a virtual world, the method comprising the steps of: storing a dialog between a user and an agent, by a processor, wherein said agent answers said inquiry about the user operation to produce a stored dialog; identifying a common node present in both said stored dialog and an additional dialog, by the processor, wherein said stored dialog and said additional dialog have a list structure in which dialog units of said user and said agent are set as nodes; connecting said stored dialog in said list structure with said additional dialog in said list structure, by the processor, to produce a created dialog in a branch tree structure, wherein said created dialog in said branch tree structure is created by merging said common node, and merging said common node comprises connecting said list structure below the common node in said stored dialog to a position below the common node in said additional dialog, or connecting said list structure below the common node in said additional dialog to a position below the common node in said stored dialog; and recording said created dialog in said branch tree structure, by the processor, thereby assisting an inquiry about user operation in said virtual world.