Marketing for Kingdom Hearts Melody of Memory has made it evident that Kairi will be the game's main character, but it's still a mystery as to how exactly she will fulfill the role. All of Melody of Memory's trailers have released already, and none of them show gameplay of Kairi — she only appears in the cutscenes.
In an interview with Famitsu, Kingdom Hearts series director Tetsuya Nomura cleared up exactly how Kairi will tie into the game's main storyline and rhythm-based gameplay. According to Nomura, Kairi will be Melody of Memory's "storyteller," and will narrate the events of each world the player visits.
For context, Kingdom Hearts Melody of Memory is more or less a recap game. It summarizes the events of the Kingdom Hearts story so far — up to the ending of Kingdom Hearts 3 Re:Mind. The player relives the series's events through its music, and Kairi will apparently assist in retelling these stories through narration.
This wasn't Nomura's original plan. Initially, he was going to have Kingdom Hearts Union Cross' Chirithy tell the story, but in the end he felt the role fit Kairi better. To compensate for the change in narrators, Nomura had to flesh out Melody of Memory's story, which is where the trailer-teased cutscenes come in.
Nomura also claims that Kingdom Hearts Melody of Memory won't have a secret movie like most other Kingdom Hearts titles. Thus the Kairi-based cutscenes will likely trigger every time a player completes a world, and the cutscene that comes after beating the game may be a hint at the series' next installment.
Kingdom Hearts Melody of Memory releases November 13 for PS4, Xbox One, and Switch.
Source: Famitsu