The Shin Megami Tensei games, and their various spinoffs, tend to provide a wealth of player agency. While this primarily comes out in the gameplay, which offers a wide variety of combat options, it has, in the past, extended to the narrative as well. Persona 4 had multiple endings, some of which involved entire dungeons you wouldn’t otherwise see. Shin Megami Tensei: Nocturne, the last main-series SMT game, involved the player remaking the entire world.
It appears that Shin Megami Tensei IV will follow suit. According to Siliconera, a recent listing for the title on a Japanese retail website indicates that choices made during the story will affect the game’s outcome in major ways. This will be supported throughout the game by various ideologies the player is expected to follow, which often conflict with one another and force the player to make some difficult decisions. This appears to go farther than just changing the ending, actually affecting the player’s path through the story itself.
It brings back memories of the first Persona game, which had an entire second plot that could be pursued if the player took certain steps early on. The “Snow Queen” plot, independent from the game’s base story, was excised from the original North American release of the game, but returned in the PSP version.