If you're looking to go full
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, you'd be best off using an SDK like Live2D or Spine Pro (will cost you).
If you're looking to emulate just what you were showing in your examples, you can easily create the desired results by emulating softbody physics on the breasts (or whatever part you want to be the squishy soft goodness) and have that attached with springs to the character. Essentially, you would 2d rig the sprite of each breast with bones, and have multiple rigidbodies on the breast to simulate a soft whole. Then, you can make it interactable by manipulating physics forces wherever the user is pointing.
To visualize this, imagine each breast is a net of oranges like pic below. The net is attached to the characters body with a spring component. Each orange is a Rigidbody2D component, and they are held together by more spring components. The net itself then would be your sprite that is deformed with the help of rigging and the magic of a skinned sprite renderer component. For the interactivity, you would then apply physics forces where the user is pointing to each rigidbody, which causes the whole net to move accordingly.
I cannot give you a step by step on how to achieve that currently, but here are some resources on softbody physics:
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(straightforward tutorial for Unity)
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(not a tutorial, more like a theoretical overview on how softbody simulation typically is achieved, very good to get an understanding on the whole procedure)
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(straightforward tutorial for Unity)
If you are running into
specific issues, I'd be happy to help! As long as it's not requiring me to write you a whole tutorial.

Good luck.