Han first appeared to die when a speeding Mercedes collided with his Mazda RX7 in “Tokyo Drift.” Han then appeared in the subsequently released “Fast & Furious 4,” “Fast Five,” and “Fast & Furious 6,” which were revealed to take place canonically before “Tokyo Drift.” The sixth “Fast” film depicts Han’s supposed car crash anew, revealing that the driver of the Mercedes was mercenary Deckard Shaw (Jason Statham).
Han remains alive in “F9” thanks to the intervention of anonymous government agent Mr. Nobody (Kurt Russell). The main thrust behind the story of “F9” involves Dominic Toretto (Vin Diesel)’s newly arrived brother Jakob (John Cena) attempting to obtain a virtual weapon called Aries. Elle (Anna Sawai) is the daughter of two scientists who once obtained and split apart Aries in order to prevent others from using it for evil. In doing so, they made Elle’s DNA key to its activation.
This fact turns out to have been the lynchpin in Han’s survival. Mr. Nobody, during his efforts to obtain Aries for himself, found out that its activation required Elle’s DNA. He thus faked Han’s death so that Han could covertly help obtain the parts of Aries and later act as Elle’s guardian.
The mechanics by which Mr. Nobody helped fake Han’s death are never detailed but can simply be explained away by Mr. Nobody’s considerable experience as a government agent. With Han now fully back in the fold, as revealed in a mid-credits scene after the film’s ending, he’s now primed to properly get revenge on Deckard Shaw for the unsuccessful but nevertheless sincere attempt on his life.