How could I make an object extend between two objects, like a line between points?

What I'm looking for can be seen here at ~4:30, with the boss 'Black Swing' and his sword being connected by an arm. I'm assuming that this was done with code and not animations, as I can't think of any way without code to do it. Help would be appreciated in duplicating this effect!

 

@CharliePatton

Arm could be just a line renderer... and sword can be moved with code or with single animation clip, or animator + state machine with several clips.

Edit: there will always be some amount of "code" you can't avoid that, even if you would do something with some visual system.