No, Chainsaw Man is not a true story. It is a fictional manga and anime. It features a lot of supernatural elements like a character having chainsaws for arms which don't exist in real life.
Well, in terms of the Chainsaw Man 146 A04 fanfic, one aspect to consider is the writing style. If it follows the same intense and fast - paced style as the original manga, it would be really engaging. The fanfic could also explore different themes like the nature of power and sacrifice which are prominent in the main story. Also, the way the author portrays the devil - hunting world in this fanfic could be quite interesting.
Chainsaw Man follows Denji as he navigates a dangerous world where devils exist. His life changes when he becomes part-devil and has to deal with powerful foes. The story has exciting fights and explores themes like friendship and survival.
There is a Chainsaw Man light novel. It offers new perspectives and adventures within the Chainsaw Man universe. It's worth checking out if you're a fan of the series.