Fuji-Hakone or Hakone pass?

Hello, I'm planning on going to Lake Kawaguchiko from Tokyo on 27th Dec, spend 2 days around the area, and then travel to Hakone on the 3rd day and back to Tokyo that night.

I know that the Fuji-Hakone pass covers a 'round trip' from Kawaguchiko to Tokyo. Does that mean that I need to travel back from Hakone to Kawaguchiko to return to Tokyo?

Or should I be getting just the Hakone pass instead?

Any help is much appreciated!

It is explained on this page:-
http://www.japan-guide.com/e/e2358_014.html

The small map is very useful.

I know that the Fuji-Hakone pass covers a 'round trip' from Kawaguchiko to Tokyo.

Not really. It covers Tokyo to Kawaguchiko to Hakone to Tokyo (or the other way around).

Does that mean that I need to travel back from Hakone to Kawaguchiko to return to Tokyo?

No.

Or should I be getting just the Hakone pass instead?

No.

Enjoy your trip!