Kuwana is in Mie.
Trains heading south towards Yokkaichi and Tsu all stop at Kuwana. Both JR and Kintetsu. On the Mie-Rapid trains, it is typically the first stop.
To return to Nagoya, it's as simple as catching a JR or Kintetsu back up there (30m on the Local JR trains, 20m on the faster Rapid trains, 20m on the Kintetsu). Or you could continue on to Yokkaichi or Suzuka (home of the Suzuka Circuit) to the south.