Tel: 0266-68-2100
Address: Ikenotaira-Hotel Shirakabako Chino-shi Nagano 391-0392
Location: Free Shuttle Bus from Chino JR Station (2.5 hours from Tokyo)  
Price: 1,500 yen (adult), 1,000 yen (child) 
Hours: Hotel Guest: 6:00-10:00, 11:30-23:00. Non-Hotel Guest: 11:30 – 20:00
Closed from: 5/3 to 5/5, 7/14 to 8/31, 12/28 to 1/5
Official site 

How to get there: From Tokyo station take the Limited Express Azusa 

They have mixed bathing areas which require you to wear swimsuits. Shirakaba resort has a variety of baths, including a Stone Open-Air Bath, Suntan Room, Bubble Bath, Cypress Bath, High-Pressure Shower, Supersonic Wave Bath and a Kaburi Bath.