Itinerary advice +/- 3 weeks in August

Hi
I am planning a trip to Japan, next August. This will be my 4th trip to Japan, so I am trying something original and slightly off the beaten path. I am planning to take a 21-day JR pass, I think it is worth it as I would like to move a lot and visit many places. Any comments/ideas for improvements for this itinerary?
D1 – Trip to Japan
D2 – Arrival in Tokyo
D3 – visit Kamakura
D4 – Go to Sendai, visit Matsushima
D5 – Visit Yamadera from Sendai
D6 – Visit Hiraizumi (maybe rent a bike), go to Morioka for the night
D7 – Go to Tawazako, rent a bike (for going around the lake), then stop at Kakunodate on the way to Akita. Akita Festival at night
D8 – Go to Aomori, following the coast, maybe stop somewhere for a side-visit? (ideas anyone ?) Nebuta Festival at night
D9 – Go to Osorezan, maybe sleep there? Anyone tried already? If not sleeping there, sleep in Aomori or Hakodate
D10 – Go to Hakodate (Shinkansen Hokkaido will work \0/ !!!), visit, go to Mount Hakodate at sunset
D11 – Go to Sapporo via Shiraoi (Ainu museum)
D12 – Visit Sapporo
D13 – Visit around Sapporo (Otaru? Yoichi? Lake Shikotsu? Shakotan? Dunno yet)
D14 – Take domestic flight to Osaka, transfer to Takamatsu, maybe stopover in Himeji (depends on what time I arrive there)
D15 – Visit Takamatsu (the famous Garden thing)
D16 – Go to Imabari, rent a bike and start Shimanami Kaido. Any ideas of hotels/minshukus/ryokans for stopping about mid-way ?
D17 – Finish Shimanami Kaido, go to Onomichi
D18 – Go to Matsue, stop for visiting Adachi Museum of Art
D19 – Visit Matsue and Izumo Taisha
D20 – Go to Osaka, maybe stop somewhere along the way for a side visit
D21 – Go to Koyasan, maybe stay overnight (but I read this was overpriced, so I dunno)
D22 – Go to Ise, visit
D23 – Go to Osaka or Tokyo (depending on my outbound flight)
D24 – Go home -_-�e

I am hesitating on the last days. Maybe instead of going to Koyasan and Ise I could stay in Osaka or Kyoto...

Thank you in advance for you inputs.

Sounds like a really busy itinerary, but fun too! If you can keep up with that pace then you'll have a great time, but be careful to plan some down time if you're the type of traveler who might burn yourself out with too much...

D8 – Go to Aomori, following the coast, maybe stop somewhere for a side-visit? (ideas anyone ?)

How about taking the famous sightseeing train Resort Shirakami from Akita to Aomori? You could stop midway at Shirakami Sanchi, a UNESCO world heritage site. Even if you didn't stop, the train in and of itself is really great!

Great trip. You do realise you are staying one many places for only a day and night. May get you worn out quickly.

Visit around Sapporo (Otaru? Yoichi? Lake Shikotsu? Shakotan? Dunno yet)
Considering the speed you are traveling at... If you have a rental car you can see all those in a day. If not I would choose any two (day and afternoon) and if you have extra time, make it three (and night).

Unfortunately, I cannot drive.... I was thinking on maybe take a bus, or maybe a tour with a local travel agency....

I know the pace is fast, So Maybe i'll discard some steps. For example, I am hesitating on keeping Matsue/Izumo.

Thank you for the 'resort shirakami' advice, it looks nice !

Izumo and Matsue are very nice places. A taste of old Japan. Kind of like Kyoto but much more cosy.
The museum and garden are also a wonder.