For a relatively small place, Kakegawa has a fair number of places to stay, probably catering to business visitors as much as to travelers. Prominent on the north side of the station, Dormy Inn Express is a very new, modern business hotel, with an ambience and facilities that place it a cut above others of its kind.
My double room was spacious enough for me and my one suitcase, but might have been a touch cramped for two people with more luggage. It was certainly comfortable and well-appointed, with memorably fluffy towels, the usual fittings of TV and fridge; you can also use the TV to make requests from reception, or to check how busy the dining room and spa are.
Elsewhere in the hotel there's a laundry room, plenty of vending machines and smoking booths - all the rooms are non-smoking - and a couple of PCs for guest use in the swish, stylish lobby. If you have your own device there's free Wi-Fi throughout, and cable internet in every room.
Just off the lobby there's a little dining room where for an extra ¥1200 you can enjoy a buffet breakfast, which I imagine is very nice. There's free coffee and corn soup available all day, you get a welcome drink on check-in, and late in the evening (from 9:30pm!) they serve complimentary ramen noodles.
Up on the top floor there's a massage room and, the main selling point for me, the public spa, open every day from check-in until 9:00am the next morning. There's a pleasantly steamy sauna, complete with TV inside, and an outdoor bath, screened off from voyeuristic pedestrians so you can bathe au naturel. It was very pleasant to sit out there in the cool morning air, watching the steam rise off the water and enjoying the view out over the castle.
Most of Kakegawa's attractions are within easy walking distance; the historical castle, palace and neighbouring Ninomaru museum, the nearby traditional residence and Stained Glass Museum, not to mention Honjo-dori, a short alley packed with tiny, cosy little bars. On the south side of the station there's the Kacho-En bird park and garden and, if you're feeling energetic, you can walk out about twenty minutes to the Shiseido Art House and Museum.
There are twin rooms and doubles available; the twins are a bit bigger and a bit more expensive, but it's still great value. It looks like prices depend also on the time of year, and how you book, but it looks like you'll be paying roughly ¥6000 to stay by yourself in a double or ¥9000 for two people in a double, or between ¥9000 and ¥13000 for a twin.