Bind a mask to the character’s face:

Step1: Add slots to the bones

Step 2: add a blueprint for mask

Step 3: Add a mask to the blueprint of the character and edit the parent class and location of mask

Do character animation on bony_take off mask(half of body):

reference :[Because there is no mask, I use glasses instead]

key the animation:

modify Graph Editor:

Bake to animated sequence and do ik rig:

Add to animation sequence, set camera, and modify the f-number:

add mask blueprint and edit its location:

Do another side of view: