These past few days, I tried to extract a model from Koikatsu and then rig the expressions in Blender. The process was really extensive. After adjusting everything, I used it to create a simple animation.
https://mega.nz/file/9mljTCiJ#jJaBiKCURb-16wius8pGusD0FNqXb1xgoUdXmwwJppg