Winter in Japan 2015

Hello Everyone,

I was hoping you can help me decide whether to get a JR Pass or not.

We enter and leave Japan via Osaka. Our trip is from January 17 (arrival of 10 pm) to January 23 (Departure of 8:40 pm).

We were thinking of going on a Domestic Flight to and from tokyo via Peach Airlines for Y9610.

My question is are the train tickets in Osaka and Tokyo expensive if we will not be buying the JR Pass? We plan to go around Osaka from the 17-20. We will stay in Hotel Universal Port the whole time because we want to spend 2 days in Universal Studios.

We plan to go to Tokyo on Jan 20 and leave early to fly back to Osaka on the 23rd. We will stay in the Shinjuku area and plan to go to Tokyo Disneyland, Sanrio Land, Diver City. Will the train tickets going around tokyo be expensive as well? Where can we get a good glimpse of Mt. Fuji at this time of the year?

Thanks!