I assume we're leaving Sanae here to give Satori a chance to inspect her, like Oarfish said. The point of bringing her down here was to have Satori take a look-see: either we do that before we leave or we leave Sanae in Satori's care and come back for her later. Taking Sanae with us defeats the purpose of bringing her in the first place unless Satori is coming along for the ride, and good luck to us selling that idea.