JR pass or not? Is the route feasible?

This is going to be my first time going to Japan. These are my rough itinerary.. I will be going to Japan at the end of Dec to Jan.
Not sure if I should get the JR pass because I�fm going for 15 days. But the 15 days JR pass is so expensive! Not sure if i should get it. I am still in a blur from Nagoya to Fujikawaguchiko. Is there an easier way to get there by public transport?
Please advise!

Will be traveling down from each points:

1. Osaka 4d3n
2. Kyoto 3d2n
3. Nagoya 3d2n
4. Fujikawaguchiko 3d2n
5. Tokyo 6d5n

Thank you

You dont need JR nationwide pass,
Regional pass is sufficient
For osaka kyoto,you can buy surutto kansai pass or kansai through pass 3 day=5400 yen
For Tokyo, you can buy greater tokyo pass 5 day=7200 yen ,cover narita airport

National JR pass is going to be too expensive. As a rule of thumb you need to do at least a Tokyo/Osaka round trip for the 7 day pass to pay off. But you are going in 1 direction only. Just buy separate tickets for the longer distances and get an IC card for the shorter distances.

If a REGIONAL pass pays off , as PP suggested depends on where you go while in Osaka / Tokyo. If you do a lot of (far) day trips, then they can pay off. If not, just use your IC card.
There are also city bus pass for Kyoto or metro pass in Tokyo. Again if they pay off depends on your actual plan.

Here an introduction:

https://www.japan-guide.com/e/e2357.html

In your case, you are simply traveling too little and too slowly to make a full JR Pass pay off. There is a ton of misinformation online out there that if you are going to Japan for two weeks, then the 14-day pass is the one you want.
BTW you don't actually have to be traveling round trip to make a pass pay off - you just have to travel far enough. Though most western tourists fly round trip through Tokyo.
For the Kansai area there are several regional passes to consider - but most are rather hard to justify unless you are using them to the very end of their coverage areas, or really riding your behind off. A Kansai Area Pass for example can be worth it if you are going to see Himeji Castle & the Kokoen Garden. You also didn't mention Nara at all and it has a number of excellent places that you should not miss. To me, you don't need all that time for Osaka either (the city is best at night), and you could take some time and go see other places too like Kobe. In the end, it all depends on where you are going. If just going between the big cities, one of the easiest to make worthwhile is the Hankyu Tourist Pass.
https://www.hankyu.co.jp/sp/global/en/ticket/information/index.html
Getting from Nagoya to the Fuji 5 Lakes is something of a pain. You can take a bus from Mishima to Kawaguchiko in about 90 minutes. But what you might consider instead is if you want to put in 3 days, you can see both Hakone and the Lakes, and both areas have some very good sights.
Not sure what you have planned at Nagoya for 3 days. Every place has something to see, but if you want, take some time and go see Inuyama - the castle there is an original (not reconstructed fake) and you can also see Meiji Mura, which really is the country's best open air museum.
https://youtu.be/ZgYDE7ujk8A

Lastly, if you are going during the end/start of the year, be sure to check all the places you want to see. Some may be closed around New Year's. A lot of restaurants will be shut down on New Year's Day as well, but convenience stores are always open and can save your life.