Review my 20 days itinerary this April

Hi,
We are 26 year old married couple, travelling to Japan for our honeymoon this April :)

We created an itinerary and we want to know if it's a good one, so please advice us. (also, some questions below the itinerary):

(*) April 9: Arriving to Kansai airport at 20:00, taking a train to Kyoto and staying there for the night.
(Day 1) April 10: Kyoto full day
(Day 2) April 11: Kyoto full day
(Day 3) April 12: Kyoto to Nara for a day trip, still staying at Kyoto for the night.
(Day 4) April 13: Kyoto half day, than going to Gero to stay there for the night. (Takayama festival tomorrow and the closest hotel i could find is in Gero).
(Day 5) April 14: Gero to Takayama for a full day for the festival and the city itself, going back to Gero for the night stay.
(Day 6) April 15: Gero to Osaka, spending the day at Osaka and also staying there for the night.
(Day 7) April 16: Get up early and travel from Osaka to Naoshima art island, spending the day there and traval from Naoshima to Hiroshima in the end of the day, staying at Hiroshima for the night.
(Day 8) April 17: Half a day in Hiroshima, Half a day in Miyajima, going back to Hiroshima for the night.
(Day 9) April 18: Hiroshima to Osaka in the morning, spending the day at universal studios, staying in Osaka.
(Day 10) April 19: Osaka to Hakone in the morning, spending the day and staying in Hakone.
(Day 11) April 20: Hakone full day, staying there also for the night.
(Day 12) April 21: Hakone to Fuji 5 lakes in the morning, spending the day and staying in Fuji 5 lakes.
(Day 13) April 22: Fuji 5 lakes full day, staying there also for the night.
(Day 14-20) April 23-29: 7 days in Tokyo, with one day trip to Nikko and one day trip to Kamakura.
(*) April 30: Flight back from Narita airport at 10:00 am

Please review and advice on my itinerary, and if you could please also consider the questions above.
1. Are we staying in some locations too long?
2. Are we staying in some locations too short?
3. Are we rushing anything or making extreme train travels that could be split better?
4. Are we missing any cool places that can be added to the itinerary?
5. Is Universal studios will be fun for us? as we are not doing any roller-coasters and waiting in lines for more than 30 minutes for an attraction will probably result in skipping it.
6 We want to watch Kabuki Theater and Sumo (even a practice if not tournament is held), where and when can we do those?

Thanks you all :)

looks quite good!
I would change day 15 Osaka to Okayama, or even better Kurashiki (what is really nice small town!).

Looks good to me. As the previous poster said, if getting up early is it something you do anyway, staying in Kurashiki would be a great idea. I came through Kurashiki recently and was very positively impressed by the small old quarter.

Regarding Kabuki, there is a Kabuki theater at Tokyo (close to Ginza) and also one in Kyoto (Gion) in both you can get tickets aimed at tourists. I.e not the entire day but just to attend a small portion. Eg 1 hour which unless you are a Kabuki fanatic should be enough.

I have not searched, but I am pretty sure both places can be found via google.

Enjoy your honeymoon in Japan!

I could still find some hotels or ryokans at Takayama either at Booking.com or by GoogleMaps. It would be better to stay in Takayama to enjoy the Night Festival on 14 April.
http://kankou.city.takayama.lg.jp/_res/projects/kankou/_page_/002/001/...

Gero Onsen is not so bad, but I would prefer Okuhida Onsen than Gero. Shin-Hotaka Ropeway for Japan Alpes could also be cool.
http://shinhotaka-ropeway.jp/

Hakone and Fuji five lakes for four nights could be too much for me. Rather, I would do overnight at Nikko both for Nikko proper and Oku-Nikko. On the contrary, all these could be doable as a day trip from Tokyo, choosing the best weather days. Otherwise, I would prefer to do a chain; e.g., Tokyo-Kamakura-Hakone-Fuji Five Lakes-Tokyo.

I would like to stay on Naoshima Island, and also on Miyajima Island, rather than city centers. More romantic, don't you think so?

It looks like you would be better to skip Universal Studios, because of long queues. Use that time for Kaubuki and Sumo.

Currently, Kabuki performances are scheduled either in Tokyo or Osaka for the coming April.
https://www.kabukiweb.net/schedule/

There are no sumo tournaments in April, but you could see Asa-Geiko at some Sumo Beyas. This one has English pages.
http://www.arashio.net/tour_e.html
http://www.sumo.or.jp/EnTicket/year_schedule/

Mt Yoshino could be in full bloom; it is one of the most famous cherry blossom viewing sites in Japan.
https://www.japan-guide.com/e/e4152.html
http://www.town.yoshino.nara.jp/kanko-event/%E5%90%89%E9%87%8E%E5%B1%B...

Your last three days are in the Golden Week. I would stay in a city during that period.
https://www.japan-guide.com/e/e2282.html

I'm with Luisp, I went on a "quiet day" in June and by 11:00/noon most rides excepting the children's ones had 1 hour long lines. I had bought an express 4 pack so it was a non issue and had there since opening, at 9:00 the park was incredibly quiet. If you really want to go, you need to be coming from someplace closer because if you are using a regular JR Pass, you're looking at 2 hours if you caught a 8:27 train or you need to pay extra for one of the 7 pack express passes.

If you can afford it, I agree with trying Booking to stay in Takayama.

I also agree Miyajima is much more scenic than staying in Hiroshima, though again it is also more pricey.

OH! And April 16th is a Monday so a lot of the museums on Naoshima will be closed. I was planning to visit Naoshima on my upcoming trip and the best day was a Monday too so now I am trying to re-work my itinerary. The Art House Project is closed on Monday (I was really interested in this), the Chichu Art Museum is closed, The Lee Ufan Museum is closed, and the Ando Museum is closed.

Perhaps if you wanted to go to USJ, you could put USJ on the 16th and then go to Naoshima another time.

Good luck!

Check here for Naoshima:
http://benesse-artsite.jp/en/general-information.html

You may be interested in Night Views https://yakei.jp/en/country.php?i=japan

Kobe Kikusei Dai https://yakei.jp/en/spot.php?i=maya
Kobe Rokko Garden Terrace https://yakei.jp/en/spot.php?i=garden
Osaka ABENO HARUKAS https://yakei.jp/en/spot.php?i=harukas
Osaka Umeda Sky Building https://yakei.jp/en/spot.php?i=sky-build

Yokohama Landmark Tower https://yakei.jp/en/spot.php?i=landmark
Tokyo Seaside Top https://yakei.jp/en/spot.php?i=trade_center
TokyoTower https://yakei.jp/en/spot.php?i=tokyotower2nd
Tokyo SKYTREE https://yakei.jp/en/spot.php?i=skytree_galleria

Probably rushing Miyajima/Hiroshima also. IF you add a night, you can then travel late the next day and overnight in Osaka, then hit Universal studios first thing in the morning.