Final Fantasy IV introduced the Active Time Battle system and a story with genuine dramatic stakes — redemption, sacrifice, shifting party members — establishing the JRPG narrative template the series built upon.
Follows: Final Fantasy III
Final Fantasy IV didn't invent the JRPG — Dragon Quest had established the form years earlier. But it demonstrated that the genre could sustain a story with emotional complexity. Cecil's guilt over attacking the village of Mist, the loss of party members like Tellah and Yang, and the twist that Golbez was being controlled — these were narrative moves that the previous games hadn't attempted. Players became invested in characters rather than the abstract project of levelling a team.
The party-as-story-instrument approach — characters joining and leaving based on plot necessity — became a JRPG convention. Final Fantasy VI expanded it with an ensemble cast. Chrono Trigger refined it. The influence runs directly from FFIV's decisions about how to use a cast of characters to serve a dramatic arc.