October/November itinerary (15 days)

Hi all,

I'm planning my 2nd trip to Japan.
Last year it was Spring so I thought this time I would like to see some of famous Japanese Autumn with it's beautiful foliage.
Previously I've spent most of time around Tokyo and Kyoto (also Kamakura, Nara, Fuji five lakes region and Hirosaki) so this time I would like to concentrate more on places I missed.

21st October Tokyo Narita - Osaka
21st - 25th 4 Night Osaka (Kyoto Jidai Matsuri)
25th- 26th 1 night Hiroshima (Himeji?)
26th - 27th 1 night Koyasan
27th -28th 1 night Magome/Tsumago
28th -29th 1 night Takayama (Shirikawa-go?)
29th - 31th 3 nights Nikko
1st - ?
2nd - 5th 3 nights Tokyo (Yokohama)
05/11 Tokyo Narita

My biggest issue is with transport between locations in Japanese Alps (Magome, Takayama etc.), they are all beautiful places but I don't want to spend most of my time in the train. I was also thinking to include Kurobe Gorge but to get there from Osaka or Kyoto and then arrive in Takayama or Magome it's not possible. I've booked only 1st hotel in Osaka so I still can reorganize whole trip if possible.
Maybe someone could advise me some other places some koyo (I know I will arrive a bit to early) or just places worth seeing in general. I've almost memorized whole webiste looking for possible places to visits but I still can't make up my mind. I'm still not sure if my itinerary is doable or I should skip/avoid some of the places.
I would appriciate any kind of help.

As reference I will mention places that made biggest impression on me last time:
Fushimi Inari Shrine
Otagi Nenbutsuji Temple
Chureito Pagoda view
Bamboo Grove in Arashiyama

I would do Koyasan before Hiroshima, that way you don't have to cross Osaka twice on your way upwards. 3 nights in Nikko is too much, usually 1 night is enough, or even can be done as a day trip from Tokyo, so you can allocate more time in the alps and not rush so much. Staying in Yokohama while in Tokyo doesn't make much sense in the way of commuting. If you want to visit Yokohama it can be done as a half day trip from Tokyo.

Thank you for reply. I will consider visiting Koyasan before Hiroshima, when I was planning this trip I was trying to delay Koyasan so I could maybe see some autumn leaves over there. As for Nikko I went there last year for one day but it was snowing snowing (in April) and we couldn't see anything. This time I thought about staying longer to do some hiking around Lake Chuzenji and generally take it easy :)

As it comes to Yokohama I just wanted to visit it while staying in Tokyo (sorry, I wasn't clear about this).

personally
I feel hiroshima needs 2 days.but a day is possible if you have a bicycle and like to rush things.
Koya doesn't have all too much to do so even wasting time by crossing osaka twice doesn't mean much. Koya autumn leaves isn't too fantastic.
Hiroshima/Miyajima has it better.
You can take the local line north from hiroshima for a few stops. Beautiful unknown temple atop a hill. Autumn leaves are good here. It is like a little piece of kyoto

After all your advices I'm thinking to spend only two days in Nikko and maybe add extra one to Hiroshima. I was also thinking about skipping Takayama and going to Kamikochi instead as it's closer from Kiso Valley.
TO be honest I was thinking about visiting Iwakuni while in Hiroshima but with one day I thought it might be a bit too much.
@ Joshua - do you remember name of the Temple or how to get there exactly?

Currently my itinerary looks like that:

21st October Tokyo Narita - Osaka
21st - 25th 4 Nights in Osaka (Kyoto Jidai Matsuri)
25th- 26th 1 night Koyasan
26th - 28th 2 nights Hiroshima
28th -29th 1 night Magome/Tsumago (visit Koka Ninjutsu Yashiki if there will be spare time)
29th - 30 1 Night Kamikochi
31th - 1st 2 nights Nikko
1st - 5th 3 nights Tokyo (sidetrips to Yokohama, Lake Kawaguchiko or Hakone)
05/11 Tokyo Narita

Thank for all help and let me know if you would change anything else.