Magome, Tsumago, Matsumoto and Kamikochi

I am trying to plan a 3-4 days around this places in early May, during Golden Week, but I am not sure about the distances and the time I will need to visit each place.
My idea for now is: Osaka-Nakatsugawa-Magome, Magome-Tsumago (hiking) and stay there (how many hours should I spend for each place?) Day 2, Tsumago-Nagiso (taxi), Nagiso-Matsumoto, stay in Matsumoto. Day 3, Matsumoto-Kamikochi (visiting the area between Taishoike and Kappabashi or between Kappabashi and Myojinbashi, and back to bus stop), then I have another doubt: staying in Hirayu Onsen/Shiraone Onsen or going to Takayama and stay there (there is the possibility the onsens will be very expensive and/or no rooms available). Day 4 visiting Hida no Sato (or Shirakawago) and in the afternoon coming back to Osaka.
What do you think? How would you plan a similar trip? And... the last question: is Kamikochi still cold in that period?

Hi, they are some of my favorites places. Kamikouchi will be very cold in April, probably still snow about. There was some snow still on the ground in May this year. I think it opens mid April, you should check. We stayed at the Onsen Hotel, the food and onsens are excellent, in fact everything about it is excellent and the staff are really nice.

Matsumoto is a bit boring (sorry) even though we've stayed there a couple of times. The castle is excellent though. I'd only stop over or stay overnight.

Takayama is really nice, so try to work that in. I like it much more than the Tsumago/Magome trail thing which was really underwhelming compared to other places. We stayed at the resort at Nagiso which was nice, but I wouldn't go back.

One place I'd add to the mix is Karuizawa. They say it is a resort but it isn't really, more a trendy town. But beyond the shops there are hikes etc and the food is awesome - two thumbs up for Tsuruya Ryokan which is situated at the start of a good hike (part of the Nakasendo trail) to the border of the Gunma/Nagano prefectures and some brilliant views.

So if it was up to me, I'd go Tokyo-Karuizawa-Matsumoto (castle only)-Kamikouchi-Takayama, and then I'd finish it off maybe in Hikone which is also part of the Nakasendo trail. That's be an awesome trip.

Thank you Lazy Pious. So during the beginning of May I should bring with me warm clothes for going to Kamikouchi?
Yes I know, Matsumoto is not a so funny city, what I want is only to visit the castle. A good idea could be to visit the castle in the morning, arriving from Nagiso, and after the castle go toward Kamikochi and stay there... what do you think?
Karuizawa is a good idea, but I come from Osaka and it is a bit far from the itinerary I am planning. But I will keep it in consideration for the next trip :)

So during the beginning of May I should bring with me warm clothes for going to Kamikouchi?

Yes, Kamikochi is alway quite a bit colder than the rest of Japan. Evenings and early mornings can be quite chilly even in the summer.

Agreed, I've only been in late May and even then there were people hiking into the peaks to cross country ski down, and sometimes it was very cold, especially when it was overcast. And the stream is from melted snow (I assume) so when I put my feet in, it was amazingly cold.