>>713580843
They could use Live 2D to animate the portraits for breathing patterns, but I don't think it's necessary.
The first 4 games HAD to use portraits for expression due to the top-down perspective being unable to showcase the chibi models. Same goes for any visual novel/gacha dialogue format where they plaster the portraits on a background that are facing the player.
RF5 started the shift to 3rd person perspective, but the pauses on each animation with a gray background for a bit. The models don't even mouthflap, the portraits do.
https://youtu.be/bf3nmLJZVOg?t=404
Azuma would either let you freely rotate the camera so you could view each facial expression, or its better cutscene direction would shift constantly to focus on each change. A few in particular I liked was Kurama's bonding event where Kai's model is sent flying into the sky, Fubuki's where you're hit with a snowball and then faceplanting the next frame, and Clarice in the ending where she's gushing over Woolies with Woolby in the background.

The artist for Azuma is some literally-who Atsushi Igarashi from HYDE Inc. who's only doing support artwork for RF5 and Digimon Survive, and I think the drafted character designs translated seamlessly into the models.
If we go back to Minako Iwasaki portraits, as series tradition, some intern's gonna fuck the coloring and line thickness again.