The cheapest package costs ¥1000 only, which gives you access to all indoor and outdoor baths. It also comes with two towels: one for use inside the baths and one for drying after. Unless you are really into hot stones and bedrocks and unless your idea of an onsen requires lounging in a a nice yukata (in which case, you ought to go for the yuttari package for an additional cost -- the price varies depending on the time and day of the week), there's enough to enjoy with the basic package.
My favorite indoor bath is the carbonated or tansan bath. The bubbles in this bath from carbonated water are invigorating. I spent the most time outside though. There were three baths to luxuriate in: a cozy rock bath, an infinity-pool style larger tiled bath, and a shallow bath to lie down on and relax supine.
The shower facilities are stocked with high quality shampoo, conditioner, body wash and facial wash. Do not miss using the collagen peel facial wash (not available in all shower stalls so look out for a stall with it). The locker room, on the other hand, has an amazing facial moisturizer that leaves your skin so silky soft, you will be tempted to purchase it at the onsen store (great marketing!). Take advantage of these high quality personal care products for a complete spa experience.
The restaurant has a buffet for an additional ¥1,580. You can continue to enjoy the view of Lake Miyazawa from the restaurant's large picture windows.
A Moomin theme park is scheduled to open in the Miyazawa lakeside area in the fall of 2018, adding yet another reason to visit this place.
Miyazawako Onsen is located at 27-49 Miyazawa, Hanno 357-0001, Saitama Prefecture. At Hanno Station of the Seibu Ikebukuro Line, go out the West Exit and catch the bus that goes to the onsen. Driving is also a convenient option as there are many parking spots available.