Advice on itinerary

Hello, I am planning to make a travel to Japan this year, preferably before June. I'm currently planning on going to Japan on a 12 or 14-day trip. This is also my first time going so I'm a little bit nervous about asking and even making this post. I've been planning this trip for the past 6 months, but I still have some doubts so any advice from experimented travelers would be very much appreciated.

My preliminary itineary is as Follow:

Day 1-4 Tokyo and Yokohama
Day 5-6 Kyoto
Day 7-9 Hiroshima (day trip to Kure)
Day 10-12 Osaka
Day 13-14 Tokyo and Return

Am I trying too much for a first time travel? Should I stick to Kanto region and just going for one far destination?
As a note I have my doubts on going to Osaka so I would like to hear if it's worth visiting?

Thanks in advance, sorry If I made any mistakes or this post is somewhat confusing....

For a 12~14-day trip, I think it is a reasonable outline.
I don't know what your plans are in Kure, but that is an unusual destination for a first timer.
On the way to Hiroshima, you can stop by Himeji if time allows.
https://www.japan-guide.com/e/e3501.html

Personally, I would spend more days in Kyoto and less in Osaka. Nara is a good side trip from either Kyoto or Osaka.
https://www.japan-guide.com/e/e2165.html

Thank You for your comments. The reason I want to go to Kure is to visit the Battleship Yamato museum that I read is located in Kure. I am a Big fan of Warships

This might not be the best of advice, but I am going to try to crush the days outside of Tokyo into 7 days. That way, you can get a 7-day JR pass for transportation, and save some money.

You mentioned going to Yokohama at the beginning of you trip, so I am going to suggest staying in a hotel near Shin-Yokohama station.

I am not even sure if it is still offered, but JR has a relatively fast Bullet Train from Shin-Yokohama station early in the morning at 6:00 AM. This would mean you would have to wake up, check out of your hotel, and get to the station to catch this train. I understand that this is not what many people might consider doing on their vacation. You will also have to check time tables, because things might have changed.

It is still almost a 4 hour train ride on the Shinkansen, but it will get you to Hiroshima early enough to go to Miyajima Island for the day.

On the next day, check out of your hotel, but have them hold your luggage. You can visit Peace Park and the Museum in Kure, before returning to pick up your luggage. You would then take a late afternoon/evening Shinkansen back to the Osaka/Kyoto area. You have used two days of your 7 day pass.

The next 5 days would be spent in the Osaka/Kyoto area. On the final day of the JR Pass, you would repeat the process of checking out of your hotel, and having the hotel hold your luggage. The final evening would have you take a Shinkansen back to Tokyo.

I am not going to suggest where and what you do in the Kansai area. I do not know your interests.

This also means more time near Tokyo, which might mean a side trip to Kamakura, Hakone, Mount Fuji, or Nikko. All of these side trips can be done with special local passes, so look into them. Once again, I do not know your interests, so I will not offer suggestions. Check out the rail passes in the transportation section of Japan Guide.

This seven days could happen any time during your trip, so I am going to suggest looking up the tides at Miyajima to optimize the high and low tides. Typically, when you are just after the full moon, there will be a high tide in late morning, and a low tide in the late afternoon. This will give you the best views of the gfloatingh shrine, and when the large Tori gate is gbeachedh.

This might not be the thing you want to do., but I hope this helps.

Good Luck in planning your trip.

Thanks for Your extensive response ebaychucky311, it's very appreciated.
It's good that You bring the JR pass, I still have doubts about buying 7 day or 14 day. I have this doubt of I can actívate when I want or of I have yo actívate right away.
About Kansai region I'm not very familiar with it but the sugestions are welcome.

Pretty standard itinerary for a first timer.

I'd merge Kyoto and Osaka together. Just stay in Kyoto and day/night trip to Osaka.

Kure will screw up about 4 hours of a day. Unless you plan on walking around and view more ships within the harbour. You may need to add a further night if that is the case.

Yeah seeing if the itinerary allows you to squeeze Hiroshima and Kyoto into 7 days makes sense. Saving a lot of money.

When you exchange the voucher for the JR Pass, you will be asked what days do you want the pass active from. If you arrive on the 3rd, you can tell them to activate the pass immediately, or say, five days on the 8th.

You should be able to start getting tickets immediately for the time period that the pass is active, so I would suggest getting the exchange done as soon as possible.

This is more important if you are traveling during a high traffic time, such as gGolden Weekh, when people are traveling a lot.

So, if you are wanting additional suggestions, you will need to be a little more specific about what your interests are, and what dates you are going.

I have some quirks, such as I went on the Chichibu Pilgrimage, and my wife is a quilter. Chichibu is close to Tokyo. Nippori Station is close to a district called gFabric Townh, and it has a direct train from that station to Narita Airport. Every time I go, my final hotel is in Nippori, so that I can purchase meters and meters of fabric to bring home to my wife. I always pack an empty duffle bag, and it is full on the plane ride home. This is what I mean by being specific. I also like trains, and I usually get a gGreenh JR pass, and try to ride several gWide Viewh limited express trains in the first car in the row of seats just behind the engineerfs compartment. You get a view out the front of the train.

Once again, good luck, in planning you trip.

I would also stay in Kyoto & day trip to Osaka. I would then either do Hiroshima to Tokyo in a day or do a one night stop in Himeji on the route back.
Btw. I have been to the Yamato museum & really enjoyed it

While in Kure, do the port tour and you can take close-up photos of JMSDF ships.
https://setouchifinder.com/en/detail/774