Below you can see the front-view size comparison of the Nikon 1 J5 and Pentax K-S2. The Nikon 1 J5 is clearly the smaller of the two cameras. Its body is 25mm narrower, 31 mm shorter and 41 mm thinner than the Pentax K-S2.
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.