Morioka to Kusatsu - pit stop city required

I am coming from Morioka and I want to go to Kusatsu.
Where can I leave my baggage? I don't really want to take it with me all the way to Kusatsu,

I was thinking of staying at Nagano, but the commute from Nagano to naganoharakusatsuguchi is 153 mins with 1 tsf.

Is there a better city to have a pit stop to drop off my luggage and go for a daytrip and come back to hotel for a night's stay?

Where can I leave my baggage?

Are you implying that you will return to Morioka afterwards? Or continue to Nagano? Please clarify your itinerary.

Assuming you do not return to Morioka and will be continuing somewhere else afterwards (Nagano?), I recommend to send your luggage by a delivery service from Morioka to Nagano. More about the delivery services:
http://www.japan-guide.com/e/e2278.html

I strongly recommend to spend one night at a ryokan in Kusatsu for fullest enjoyment of the town.

I am not going back to Morioka. My plane departs in Haneda.

Uji, I like your suggestion of staying overnight in Kusatsu.
Do you have a recommendation for a nonsmoking hotel, inexpensive but decent. I usually stay at Toyoko Inn.

If you're going Morioka - Kusatsu - Narita - home I'd suggest takyubin- ing your luggage to Narita from Morioka.

I recommend to stay at a traditional ryokan with tatami rooms as close to the yubatake as possible. One of my favorites is the Naraya:
http://www.booking.com/hotel/jp/naraya-kusatsu.en-gb.html?aid=355588

It is much more expensive than a Toyoko Inn, but I think the special experience may be worth the special expense for one night. If the budget does not allow, it there are some less expensive ones in the surroundings, as well. I recommend to look at the listings in Bookings.com or other online reservation sites. Again, I recommend a place in walking distance to the yubatake.