Which rail.pass should I get

We are four seniors travelling into Narita on 23 and travelling to Karuizawa from 23 to 28 Dec.

We will return to Tokyo on 28 Dec. We will stay in Tokyo 28 Dec to 2 Jan.

On 2 Jan Wwe will travel from hotel in Tokyoback to Narita to board a flight back home.

Should we get a rail pass and which one?

Thank you very much.