Kamisato Service Area (Kamisato SA) is a well-equipped rest area in Saitama Prefecture. Highway buses heading to Karuizawa and Kusatsu Onsen make a stop here.

Kamisato SA has bathrooms, nursing rooms, free tea and water dispensers, ATMs, and a variety of souvenir shops. There are also a few restaurants serving food like ramen and curry-rice sets for a quick meal. In addition, there are EV charging stations.
Note that there are two sides: one that buses stop at on the way out from Tokyo (outbound), and the other where buses stop when returning to Tokyo (inbound). The shops and layout vary slightly, but the facilities available are generally the same. However, the inbound service area seems to have a larger variety of souvenirs from neighboring prefectures — so you can afford to procrastinate your souvenir shopping until the very last minute!