A long story narrating a series of complicated events is called a

Explanation

A saga is a long story, often a narrative, that recounts the deeds and adventures of heroic or legendary figures or the history of a nation. It is a term used in literature to describe a long narrative, often in prose, that tells of the adventures and heroic exploits of a group of characters. The other options do not fit the definition of a long story narrating a series of complicated events.