My plans 5 days japan 1 korea
 

Hi, I want to ask if my plans is okay cuz I'm going to japan for first time
I will arrive tokyo 31/8 at night so I put plans like this
1/9 visit askasa &moomin cafe , in the night tokyo tree or sky
2/9 visit fuji mountain and trip around it
3/9 take the day in kyoto
4/9 go to akihibara
5/9 travel to seoul and back in the night
6/9 visit park & shopping
7/9 my flight will be at night
Is this okay ??

Honestly, it's not how I would plan a trip. A day trip to Kyoto? Not worth it, in my view. Take your time from Sept 6 and make it 2 days at the very least. Look into getting a Japanican discount ticket:
http://www.japanican.com/en/tour/detail/VJOPENTK1/
You can take the fastest bullet train with it, the Nozomi, so that will give you a little more time.

For Sept 2nd you need to be more specific - to see My Fuji (which is very iffy at best in the summer) you can go to either Hakone
http://www.japan-guide.com/e/e5200.html
or the Fuji 5 Lakes area.
http://www.japan-guide.com/e/e6900.html
Both have similar things to see but are not the same. At least there is more to do if the weather obscures the view.
Look into getting one of the Odakyu passes for going there.
http://www.odakyu.jp/english/deels/

For Sept 4th it is too empty. You can see Akihabara in a couple hours tops, unless you really want to go shopping in every store for something specific. See some parks or other areas too.
http://www.japan-guide.com/e/e3034.html

And a day trip to Seoul? There are cheap low cost carriers there, and the flight time is not long, but again, not worth it. Save it for a future trip.

I'd cut the day trip to Seoul - as above, save it for next trip.

I'd want at least three full days in Kyoto (actually more, but you don't have the time).

I agree
-- skip the day trip to Seoul (it easily warrants several days, and you are barely scratching the surface of anything in Japan) and
-- don't do a day trip to Kyoto. Either skip it or split your time between Tokyo and Kyoto (I wanted 6 days for my first visit to the Kyoto area).

Spend some time with japan-guide.com. If you decide to spend all your time in or near Tokyo, you have lots of options to keep you busy all day every day in the city or with some day trips in the area nearby (e.g., Kamakura or Nikko).

Good luck!

Yep, same as everyone above.

A day trip to Kyoto from Tokyo is not recommended, have you understood the distances and travel time involved?

And likewise, a day trip to Seoul doesn't make any sense. I know the world looks small on a globe but an international flight, with minimum check in times, travel time and then getting to the destination from the arrival airport - would leave you no time to see or do anything!

If you have only 6 nights, then decide whether or not Kyoto and Tokyo are your top priorities and split the nights between. I'd suggest either Kyoto 4, Tokyo 2 or 3 nights in each.

Alternatively, you could do all the time in one or the other, and make day trips to extend what you see. From Tokyo, you have Nikko, Kamakura, perhaps even Hakone. Or from Kyoto you could visit Nara, Osaka, Uji and many others.