Need help with sword attack direction based on mouse movement (+video example)

This isn’t something easy to do for beginners but we highly encourage you to learn more.
To achieve something like that, there are a couple of stages that you need to do.

Here’s some pointers/area that will help you with this. Do some findings on these and I’m sure you will get what you wanted.

  1. Use animation layered per bone functionality to separate lower and upper body animations.
  2. Implementation of aim-offset functionality so that the character will always follow the camera rotation/location.
  3. Play attack montage on the upper body and locomotion animation on the lower body.
  4. Check if the camera is at 180-degree rotation (looking back) and rotate the character afterwards. You can find this on the Youtube tutorial as well.

Again, this is a huge topic to cover, but with some dedication and effort to do some study on these listed pointers, I’m sure you will learn better.
Hope it helps.